根据下面一篇短文的内容判断所给句子的正误, 正确的用“A”表示，错误的用“B”表示。

This is a special class. The students come from different countries. Some come from America, others come from Canada, Japan,Australia and England. They speak different languages. But all of  them can speak English. They're good friends. They study together,play together and live together. They help each other.

All the teachers of this class are Chinese, but they can speak English. They teach their students in English. They're very kind and friendly. They work hard. The students in this class study Chinese cooking and Chinese kongfu. All the students like China. They say China is a great country and the Chinese are friendly, and they're happy in China.

小题1:The students all come from England.

小题2:All of them speak the same language.

小题3:The teachers of this class teach their students in English.

小题4:The students in this class only study Chinese cooking.

小题5:The teachers of this class can speak Chinese and English.

已知A、B、C、D的原子序数都不超过18，它们的离子_aA^(n＋1)＋、_bB^n＋、_cC^(n＋1)－、_dD^n－均具有相同的电子层结构，则下列叙述正确的是（）

A. 原子序数：a＞b＞c＞d

B. 离子半径：A^(n＋1)＋＞B^n＋＞C^(n＋1)－＞D^n－

C. 离子还原性：A^(n＋1)＋＞B^n＋，离子氧化性：C^(n＋1)－＞D^n－

D. 单质还原性：B＞A，单质氧化性：D＞C