The primary reason for withholding food and fluids from a client who will receive general anesthesia is to help prevent

A. constipation during the immediate postoperative period.
B. vomiting and possible aspiration of vomitus during surgery.
C. pressure on the diaphragm with poor lung expansion during surgery.
D. gas pains and distention during the immediate postoperative perio

下列四种结构形式的电磁系统，吸力特性最陡峭（）。

A.U型直动式

B.E型拍合式

C.U型拍合式

D.甲壳螺管式