—— How many students are there in your class?
—— There are twenty students in our class, five Americans.
A:including
B:improving
C:discussing
①2个氮原子:____;
②1个钙离子:____;
③氖气:____;
④铁离子:____;
⑤5个硫酸根离子____.
I like ________ story books, but my friend Alice likes ________ TV shows.
下列句子标点符号使用不正确的一项是( )
读下列某地地质灾害成灾频次示意图,完成下列小题。