Historically, cities have often originated and thrived because they we

Question

Historically, cities have often originated and thrived because they were centers of trade. From the first national census in 1790 through the 1960 census, the ten most populous cities in the United States were all located on navigable waters. In 1970, Dallas, which is nowhere near navigable water, made its first appearance in the top ten. In the 2010 census, three of the ten most-populated US cities were landlocked. Therefore, trade must not be as important a determinant of city growth as it used to be.
On which of the following assumptions does the argument depend?

A. Geological changes can result in shifts in the locations of navigable waters. 
B. Access to navigable waters is a necessity for a city to develop thriving trade. 
C. Trade does not necessarily depend upon the movement of physical goods. 
D. The presence of high-tech industries is now more important than trade in the growth of cities. 
E. Population shifts to warm, dry Southern states overshadowed the importance of trade.

VBudhew · Answer

The Argument is all about "the trade is not as important for determinant of city growth as it used to be"
==>> the passage says about navigable waters (for moments of goods because we are talking about trade) therefore we can say that . Trade does not necessarily depend upon the movement of physical goods.
therefor i choose C

sahilsh · Answer

Cities originate and thrive -> Thanks to trade
Hence all 10 top cities initiatively had access to navigable waters.

Later cities without access to navigable water started originating and thriving.

Premise: Trade started becoming less important.

Assumption: Trade is possible only with navigable water.

Let's attack assumption to be double sure: Trade initially was possible only through water but later land and Air trade added to it and cities like Dallas had access to later two and hence thrives. Premise falls.
Hence B is the answer

VBudhew · Answer

sahilsh Thanks for replying but in my opinion the argument is talking about "cities growth and trade" and there are hardly in options considering or bridging the gap for this conclusion with the premises given, Option B looks good to fill the gap between its own premises and not the conclusion.

can you please elaborate the approach?

can you please elaborate the approach?

VBudhew · Answer

So basically if we think from the perspective of comparison of cities in the past and cities in the present we need to keep all the parameters of the comparison equal and thus in this case we can say that for current " Access to navigable waters is a necessity for a city to develop thriving trade." as it was used to be.

if we go in this way B is far better choice than C...but still I'm not getting over C

buan15 · Answer

Official Explanation:

Step 1: 
This is an Assumption question. Determine what unstated assumption is necessary for the argument to make sense.

Step 2: 
From 1790 until 1960, the ten most populated cities in the United States all had access to navigable waters. Since 1970, three cities without access to such waters have joined the top ten. All of this is evidence for the author’s conclusion thattrade is not as important a determinant of population as it was in formerdecades.

Step 3:
The evidence is about cities’ proximity to navigable waters; the conclusion is about trade status. The assumption bridges this scope shift: the author assumes that proximity to navigable waters is a necessary condition for a city to become a trade center and, as a result, to grow.

Step 4: 
Choice (B) is a good match for this prediction and is the correct answer.
Shifts in navigable waters, choice (A), are irrelevant to the author's argument (even if they actually do occur).
If choice (C), which states that trade doesn’t depend upon actual movement of goods, is true, then the cities that are new arrivals to the top ten may actually be trade centers. But in that case, the conclusion divorcing city growth from trade has nothing to stand on.
Choice (D) may be tempting because it posits that something other than trade has become more important to growth, but it does not correspond to the assumption made in the stimulus—instead, it merely makes the conclusion more specific.
Similarly, choice (E) again posits that something (this time, a shift in population) is more important than trade, but this again merely adds specificity to the conclusion, which already says that trade isn’t as important to city growth as it used to be.

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Kremlin213 · Answer

If B is true then it will falsify the Dallas originating and thriving why not C

singhaz · Answer

Historically, cities have often originated and thrived because they were centers of trade . From the first national census in 1790 through the 1960 census, the ten  most populous cities  in the United States were  all located on navigable waters.  In 1970, Dallas, which is nowhere near navigable water, made its first appearance in the top ten.  In the 2010 census, three of the ten most-populated US cities were landlocked.   Therefore, trade must not be as important a determinant of city growth as it used to be. 
On which of the following assumptions does the argument depend?

A. Geological changes can result in shifts in the locations of navigable waters.
 B. Access to navigable waters is a necessity for a city to develop thriving trade. 
C. Trade does not necessarily depend upon the movement of physical goods.
D. The presence of high-tech industries is now more important than trade in the growth of cities.
E. Population shifts to warm, dry Southern states overshadowed the importance of trade.

himssss29 · Answer

Answer: B

Premises: 
 
 Historically top cities were on navigable water 
 From 1790-1960 ALL top 10 cities were on navigable water 
 1970: Dallas (landlocked) entered top 10 
 2010: 3 of top 10 cities are landlocked  
 Conclusion: 
Trade is less important for city growth than it used to be

Gap: 
The argument silently assumes that  navigable water = only way to do trade . Without this link, landlocked cities growing tells us nothing about whether trade matters less!

A. Geological changes shift navigable waters  ❌
Completely irrelevant — argument is about trade importance, not geography changing
 B. Navigable water necessary for trade  ✅
This is the exact missing link — connects "no water" to "less trade" to "trade less important"
 C. Trade doesn't depend on physical goods  ❌
This actually HURTS the argument — if trade doesn't need physical movement, landlocked cities can still thrive through trade, meaning trade is still important!
 D. High-tech industries more important than trade  ❌
This is the conclusion itself dressed up differently — an assumption can never be the same as the conclusion
 E. Population shifts to warm southern states  ❌
New idea never mentioned in argument — introduces climate/geography as explanation, completely out of scope.

Historically, cities have often originated and thrived because they we

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