下列哪项不是引起机械性肠梗阻的原因（）。 A.肠管扭转 B.肿瘤 C.肠道闭锁 D.

肠套叠的典型X线征象是

A．出血速度快，呕血或便血
B．出血速度较慢，便血为主
C．出血伴腹痛，高烧
D．少量便鲜血
E．腹痛、发热、黄疸

若等比数列{a_n}的公比q＞0，且q≠1，又a₁＜0，那么（　　）

A．a₂+a₆＞a₃+a₅

B．a₂+a₆＜a₃+a₅

C．a₂+a₆=a₃+a₅

D．a₂+a₆与a₃+a₅的大小不能确定

定量分析工作要求测定结果的误差（）

A.越小越好

B.等于零

C.在允许误差范围之内

D.略大于允许误差

E.随操作人员熟练程度而定

用所给词的正确形式填空

1. —Who is your _______ (close) person in your family?  

    —My grandmother is.

2. —Whose coats are these?

    —They are the _______. (run)

3. She didn’t get better grades because of _______ (play) games too much.

4. He jumped _______ (far) than the others and he won the first prize.

5. Our teacher is so_______(humour) that we all like him.