—______ does your father often go to work?
—By bus. [ ]
A. When
B. How
C. why
D. Where
答案:B
上腹部束带状疼痛,多呈持续性
A.急性胆囊炎 B.急性阑尾炎 C.胃、十二指肠溃疡穿孔 D.急性胰腺炎 E.右输尿管结石
离心方法主要有差速离心,(),()。