题目内容：

    There are two kinds of memory: short-term and long-term. Information in long-term memory can be remembered at a later time when it is needed. The information may be kept for days or weeks. However, information in short-term memory is kept for only a few seconds, usually by repeating the information over and over. The following experiment shows how short-term memory has been studied.

Henning studied how students who are learning English as a second language remember vocabulary. The subjects in his experiment were 75 college students. They represented all levels of ability in English: beginning, intermediate (中等), and native speaking students.

To begin, the subjects listened to a recording of a native speaker reading a paragraph in English. Following the recording, the subjects took a 15-question test to see which words they remembered. Each question had four choices. The subjects had to circle the word they had heard in the recording, some of the questions had four choices that sound alike. For example, weather, whether, wither, and wetter are four words that sound alike. Some of the questions had four choices that have the same meaning. Method, way, manner, and system would be four words with the same meaning. Finally the subjects took a language proficiency test.

Henning found that students with a lower proficiency in English made more of their mistakes on words that sound alike; students with a higher proficiency made more of their mistakes on words that have the same meaning. Henning's results suggest that beginning students hold the sound of words in their short-term memory, and advanced students hold the meaning of words in their short-term memory.

1.Which of the following statements is TRUE according to the passage?

A.Henning gave a separate test on vocabulary to his students.

B.Long-term memory can be achieved only by training.

C.It is easier to test short-term memory than long-term memory.

D.Information in short-term memory is different from that in long-term memory.

2.The word "subject" in the passage means _________.

A.the theme of listening material B.the student experimented on

C.a branch of knowledge studied D.a native speaker

3.From Henning's result we can see that ________.

A.advanced students always remember words by their meaning

B.beginners have difficulty distinguishing the pronunciation of words

C.it is difficult to remember words that sound alike

D.it is difficult to remember words that have the same meaning

4.The passage centers on ________.

A.an experiment on students B.two kinds of memory

C.short-term memory D.memory