【题目】根据短文内容，选择最佳答案。
Many students in China are learning English. Some of these students are small children. Others are teenagers(十几岁的青少年). Many are adults. Some learn at school, others study by themselves. A few learn English language (语言)over the radio, on television, or in films. One must work hard to learn another language. Why do all these people want to learn English? It is difficult to answer that question. Many boys and girls learn English at school because it is one of their subjects. They study their own language and maths and English ... Some people learn English because it is useful for their work. Many people often learn English for their higher studies, because at college or university(大学) some of their books are in English. Other people learn English because they want to read newspaper and magazines in English.
（1）Many students in China are learning English, aren't they? ____.
A.No, they aren't
B.No, they are
C.Yes, they are
D.Yes, they aren't
（2）If one wants to learn another language well, he must ____.
A.learn at school
B.study by himself
C.work hard
D.study harder
（3）The sentence "It is difficult to answer that question" means ____.
A.that question is not difficult to answer 
B.that question is difficult to answer it
C.it is difficultly to answer that question
D.it is hard to answer that question
（4）What's the Chinese of "study by themselves"?
A.和他们一起学习
B.自学
C.向他们学习
D.通过学习