people differ in their working-memory capacity. b. memory acquisition depends on previous knowledge, and everyone has different knowledge. c. some people have foolish ideas about how to proceed when they really want to memorize something. d. researchers do not agree on the best ways to test memory.

The question is incomplete. The complete question is :

It is sometimes difficult to predict memory performance outside of the lab because :

a. people differ in their working-memory capacity. b. memory acquisition depends on previous knowledge, and everyone has different knowledge. c. some people have foolish ideas about how to proceed when they really want to memorize something. d. researchers do not agree on the best ways to test memory.

b. memory acquisition depends on previous knowledge, and everyone has different knowledge.

Explanation:

The working memory is defined as a cognitive system within a limited capacity which holds the information temporarily. This memory is important in reasoning as well as in the guidance of decision-making and also behavior.

The working memory is a part of the short term memory.

The long term memory stores information in our memory for a longer and extended period of time. It is a lasting memory.

The memory storage and acquisition is different for different people and the acquisition of memory depends on the previous knowledge of the person, so it relatively difficult to predict the memory performance outside the lab.

Hence the correct option is (b).

I have no idea who will actually win,  but I sure hope its not him.