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555-605 Level|   Assumption|      
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Bunuel
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Since 1941 Los Angeles has drawn water from mountain streams that feed 18 May 2022, 08:38
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78% (01:38) correct 22% (02:04) wrong based on 233 sessions

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Since 1941 Los Angeles has drawn water from mountain streams that feed into Mono Lake. If water continues to be drawn from the streams at the present rate, in about 30 years the resulting drop in the water level of Mono Lake will trigger a chain reaction ending in the destruction of the ecosystem of the lake.

Which of the following is an assumption on which the prediction is based?


(A) Since 1941 the ecosystem of Mono Lake has changed significantly as a result of a drop in the lake’s water level.

(B) The amount of water that evaporates from Mono Lake has increased annually since at least 1941.

(C) Los Angeles is investigating the availability of a different source of water that could supplement the water it draws from the mountain streams.

(D) Voluntary water conservation will not by itself be sufficient to hold Los Angeles’ water needs to present levels.

(E) Any water flowing into Mono Lake from sources other than the mountain streams will be insufficient to prevent the triggering event from occurring.
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E
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Since 1941 Los Angeles has drawn water from mountain streams that feed 18 May 2022, 11:02
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Bunuel
Since 1941 Los Angeles has drawn water from mountain streams that feed into Mono Lake. If water continues to be drawn from the streams at the present rate, in about 30 years the resulting drop in the water level of Mono Lake will trigger a chain reaction ending in the destruction of the ecosystem of the lake.

Which of the following is an assumption on which the prediction is based?


(A) Since 1941 the ecosystem of Mono Lake has changed significantly as a result of a drop in the lake’s water level.

(B) The amount of water that evaporates from Mono Lake has increased annually since at least 1941.

(C) Los Angeles is investigating the availability of a different source of water that could supplement the water it draws from the mountain streams.

(D) Voluntary water conservation will not by itself be sufficient to hold Los Angeles’ water needs to present levels.

(E) Any water flowing into Mono Lake from sources other than the mountain streams will be insufficient to prevent the triggering event from occurring.
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IMHO (E)

The gap here is -

Quote:
Water flow from mountain streams that feed into Mono Lake+Contunue for 30 more years ------->Destruction of the ecosystem of the lake.
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Only option (E) bridges the gap in both the ends :

Any water flowing into Mono Lake from sources other than the mountain streams will be insufficient to prevent the triggering event from occurring
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Since 1941 Los Angeles has drawn water from mountain streams that feed 16 Apr 2023, 12:08
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KarishmaB

although option e is correct

why not option A
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Since 1941 Los Angeles has drawn water from mountain streams that feed 17 Apr 2023, 08:35
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Bunuel
Since 1941 Los Angeles has drawn water from mountain streams that feed into Mono Lake. If water continues to be drawn from the streams at the present rate, in about 30 years the resulting drop in the water level of Mono Lake will trigger a chain reaction ending in the destruction of the ecosystem of the lake.

Which of the following is an assumption on which the prediction is based?


(A) Since 1941 the ecosystem of Mono Lake has changed significantly as a result of a drop in the lake’s water level.

(B) The amount of water that evaporates from Mono Lake has increased annually since at least 1941.

(C) Los Angeles is investigating the availability of a different source of water that could supplement the water it draws from the mountain streams.

(D) Voluntary water conservation will not by itself be sufficient to hold Los Angeles’ water needs to present levels.

(E) Any water flowing into Mono Lake from sources other than the mountain streams will be insufficient to prevent the triggering event from occurring.
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LA draws water from streams that go into Mono Lake.
If present rate of drawing is maintained, in 30 years, the drop in the water level of Lake will cause destruction of its ecosystem.

It is a conditional conclusion - if the current rate of withdrawing is maintained (ie. rate of withdrawing is not reduced) then drop will occur in water level that will destroy the ecosystem.

Highlighted is the condition which if met, will lead to destruction. It only talks about withdrawing water. But the assumption here is that nothing will add additional water in the Lake to prevent that drop from occurring.
Hence (E) is correct.

(A) Since 1941 the ecosystem of Mono Lake has changed significantly as a result of a drop in the lake’s water level.

We do not know how the Lake has changed from 1941 to present. In fact, the argument says that in 30 years, the drop in water level will trigger a chain reaction that will end in destruction of the ecosystem. So till now that trigger has not happened. We don't even know whether the Lake's water level has dropped yet or not. It may be expected to start dropping soon but may not have started dropping just yet. So how things have changed from 1941 to 2023 we do not know. All the argument is discussing is how they could change in the next 30 years.
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