Answer:
Correct answer is A. To scorch the earth by burning their crops and villages so Alexander's army would starve on their conquest.
Step-by-step explanation:
A is correct answer as Memnon knew that Persians didn't have chance if they were to fight Macedonian army in open battle. That is why he advice Darius to tell his satraps to destroy the land and crops so that Alexander's army would be deprived of resources.
B is not correct answer as he knew that Alexander will crush Persian army.