We learn from the passage that conditions for the early whites traveling to America by ships were much better than ______.

A．sick friend.
B．A math class.
C．School policy.
D．The man’s test.

A．To study how students remember English vocabulary by short-term memory.
B．To study how students learn English vocabulary.
C．To study how to develop student’s ability in English.
D．To study how long information in short-term memory is kept.