根据语境，填写适当的词语或句子补全对话。

A:  Hi, Tom. Why 1.        _  you do PE today?

B:  I have broken my arm.

A:  2.        _  did you do that?

B:  I fell off my bike.

A:  Sorry to hear that.  3.        _?

B:  Yes. I went to the clinic yesterday, and the X-ray showed that my arm was not serious.

A:  OK. Why do you 4.        _?

B:  Because I'm afraid I'll miss more lessons and I'll be left behind.

A:  Don't worry. Just take care of yourself. I think I can 5.        _  you.

B:  Thank you.

血管外溶血的特征是（）

A.急性病程多见

B.少见肝、脾大

C.尿含铁血黄素常为阳性

D.少见红细胞脆性改变

E.急性加重时可见骨髓再障危象