瘤胃手术过程中，从污染术转为无菌术的一步是______。
A．打开腹腔 B．瘤胃同定 C．瘤胃切开D．胃壁缝合第二层 E．皮肤切开
参考答案：D
Please lock the door;______, bring the umbrella to me. It looks as if it is going to rain.
A．as a result
B．in return
C．in addition
D．as well
简述GSM与第一代模拟移动通信相比的优势
