应选择哪项手术方案
A.乳癌根治切除术
B.扩大乳癌根治切除术
C.单纯左 * * 切除术
D.改良乳癌根治切除术
E.保留 * * 的乳腺癌切除
参考答案:A
— Cindy, dinner is ready, where is John?
— He ______ his homework in his room. [ ]
A. does
B. did
C. is doing
D. will do
气瓶不能用到无气,应保留余压。