局麻药对心血管系统的毒性反应是
A.血管收缩,心脏抑制
B.血管收缩,心脏兴奋
C.血管扩张,心脏兴奋
D.血管扩张,心脏抑制
E.对心血管系统无任何病理性损害
参考答案:D
—What's on the desk?
—There ________ a ruler and two pens on the desk.[ ]
A. is
B. are
C. am
D. be
树脂的储存应()。
A.混合存放
B.防止霉变
C.不怕受冻
D.不怕受热