If two students, Sarah and Tom, swap their positions in a ranking of 40 students, and Sarah is currently 10th from the top, what will be her new rank from the bottom if Tom is 31st from the top?
Answer: B. 29th
After swapping, Sarah's new rank from the top will be 31st (Tom's original rank). Her new rank from the bottom will be 40 - 31 + 1 = 10.