rs47 wrote:
Heavy salting of Albritten's roads to melt winter ice and snow began about 20 years ago. The area's groundwater now contains approximately 100 milligrams of dissolved salt per liter. Groundwater in a nearby, less highly urbanized area, where little salt is used and where traffic patterns resemble those of Albritten 20 years ago, contains only about 10 milligrams of dissolved salt per liter. Since water that contains 250 or more milligrams of dissolved salt per liter tastes unacceptably salty,continuing the salting of Albritten's roads at its present rate will render Albritten's groundwater unpalatable within the next few decades.
Which one of the following, if true, most seriously weakens the argument?
(A) Even water that contains up to 5,000 milligrams of dissolved salt per liter is safe to drink.
(B) The concentration of dissolved salt in Albritten's groundwater is expected to reach 400 milligrams per liter within a few decades.
(C) Salting icy roads is the simplest way to prevent accidents on those roads.
(D) Albritten's groundwater contained roughly 90 milligrams of dissolved salt per liter 20 years ago.
(E) Salting of Albritten's roads is likely to decrease over the next few decades.
Our goal is to weaken the highlighted part of the sentence - Show that continuing salting of Albritten's roads will not render Albritten's groundwater unpalatable
(A) Safety is out of scope
(B) Dissolved salt of 400 milligrams per liter will render Albritten's groundwater unpalatable
(C) Simplest way of prevention of accident is out of scope of the discussion presented in the stimulus.(D) This is itIf 20 years ago there was 90 milligrams of dissolved salt per liter
Now after 20 years there is 100 milligrams of dissolved salt per liter
Then within 20 years 10 milligrams of dissolved salt per liter has accumulated..
Or, within next 10 years (Decade) 5 milligrams of dissolved salt per liter will accumulate..
Now concentration of of salt is 100 milligrams of dissolved salt per liter
In a decade at the same rate 5 milligrams of dissolved salt per liter will be added and thus the concentration will be 105 milligrams of dissolved salt per liter
105 milligrams of dissolved salt per liter < 250 or more milligrams of dissolved salt
Thus salting Albritten's roads at its present rate will not render Albritten's groundwater unpalatable.(E) Reduction in rate of salting is a general comment and the statement can not attack the conclusiion...
Hence answer will clearly be option (D)