成人心肺复苏操作时,吹气和按压比例约为()
A、3:30
B、1:15
C、2:30
D、1:18
参考答案:C
We tried ________ to persuade him to stay home, but at last, he went to the construction site in spite of
his bad illness.[ ]
A.in effect
B.in vain
C.in fact
D.in addition
双螺条混合机处理粉化的原因有哪些?