Please choose the correct answer to the question: Sandra puts some pill bugs into an open box. She covers half the box with a piece of cardboard. She then places the box outside on a summer day, and all the pill bugs move under the cardboard. The pill bugs are most likely responding to which of the following?

Answer1: air pressure Answer2: bright light Answer3: wind Answer4: fog

Answer format: answer1/answer2/answer3/answer4