下列各句子中均有一处错误，请找出并改正。

1. He kept the boy to stand there for hours.                                            _______________

2. Students can't be made study all day.                                                  _______________

3. The teacher told John get his notebook in the office.                            _______________

4. Don't let children to play in the busy streets. It's dangerous.                 _______________

5. Mrs Pan makes her son practices playing the piano after school.          _______________

有关缺铁性贫血，错误的叙述是()

A．以小红细胞为主

B．以低色素性红细胞为主

C．红细胞中央淡染区消失

D．红细胞大小不一

E．可见环形红细胞