Detailed Instructions: Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
Q: Problem: a student chose a number, multiplied it by 2, then subtracted 138 from the result and got 102. what was the number he chose ?
Options: a. 90, b. 100, c. 120, d. 160, e. 200
A:
c