Teacher:You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
Teacher: Now, understand the problem? Solve this instance: A girl walked for 30 minutes. She noticed that she traveled farther in the first 15 minutes of her walk than in the second 15 minutes. What can she conclude about her walk?
(A) She walked over many hills. (B) Her average speed was faster during the first half of her walk. (C) She walked in two different directions. (D) She was walking at a constant speed.
Student:
B