Teacher:In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").
Teacher: Now, understand the problem? Solve this instance: Some people put metal tags on their dog's collars, because in darkness, these collars can (A) melt wax (B) reflect light (C) read books (D) stain clothes
Student:
B