What is the passage mainly about

A．Information in short-term memory is different from that in long-term memory only in content.
B．Long-term memory can be achieved only by training.
C．It is easier to test short-term memory than long-term memory.
D．Henning gave a test on vocabulary to his subjects.

A．All of them disagreed with him.
B．Some of them disagreed with him.
C．There was no reaction.
D．There was no response.