instruction:
You are given a mathematical question described with an open-ended vocabulary. Questions in this task involve real-world situations, describing a mathematical problem. You are also given 4 or 5 answer options (associated with "A", "B", "C", "D", "E"). Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'. LaTeX mathematical format (the standard way to express mathematical expressions in the typesetting software known as LaTeX) is used to express equations. Each question is solvable with high school math knowledge. Give only one answer for each question.
question:
After 21 students were added to a class, there were four times as many students as before. How many students were in the class before the addition?
(A)3 (B)7 (C)11 (D)14 (E)17
answer:
B

question:
There are 5 red, 5 green, 5 blue, and 5 yellow hats packaged in 20 identical, unmarked boxes, with 1 hat per box. What is the least number of boxes that must be selected in order to be sure that among the boxes selected, 4 or more contain hats of the same color?
(A)4 (B)8 (C)9 (D)12 (E)13
answer:
E

question:
A radio station emits a signal that can be received for 60 miles in all directions. If the intensity of the signal is strengthened so the reception increases by 40 miles in all directions, by approximately how many square miles is its region of reception increased?
(A)6,300 (B)10,000 (C)10,300 (D)20,000 (E)31,400
answer:
D