You are given a short paragraph, a question and two choices to answer from. Choose the correct answer based on the paragraph and write the answer(not the key).

Let me give you an example: Paragraph: Many of the worlds people live with water scarcity, and that percentage will increase as populations increase and climate changes.
 Question: John's town used to have lots of water, back when there were only a few hundred people. However, now that the town holds several thousand people, the water availability is 
 Choices: A)scarce 
B)plentiful
The answer to this example can be: scarce
Here is why: Based on the information given in the paragraph, population growth will make water more scarce, so that is the correct answer.

OK. solve this:
Paragraph: Smaller tributary glaciers, like tributary streams, flow into the main glacier in their own shallower U-shaped valleys.
 Question: Reid notices that tributary glaciers make U-shaped valleys when flowing. A large valley was likely caused by a _____ tributary glacier. 
 Choices: A)small 
B)large
Answer:
large