The answer is A: An opening at least 30 inches high and 18 inches wide in any wall or partition.
An opening in a wall or a partition is defined as an opening 30 inches or more high and 18 inches wide through which persons may fall. A wall opening includes a chute opening or a yard-arm doorway. Wall openings are easy to make since they do not have to go to elevation to manage its size.
First you read the question and numbers, then you use the numbers in the correct way and you try reallllyyy hard, you will find your answer! Hope this helps! :D