Answer:
B. How important memory strategies can be
Step-by-step explanation:
by describing these techniques as "a lifesaver" the author is saying they are very important.
A Cannot be true because the author is saying that being able to use these strategies is a valuable thing not something that is too heavily relied on.
C cannot be true because this statement has nothing to do with the frequency at which people use memory strategies.
D cannot be true because the author is expressing that memory strategies can be essential so the importance is not exaggerated.