采用液力挺柱可以消除气门间隙。
参考答案:对
When you finish reading the book ,you will have ______better understanding of ______life. ,
A.a, the
B.the . a
C./,the
D.a,/
正常人静息状态下,呼吸频率是()
A.12~16次/分
B.16~18次/分
C.12~18次/分
D.15~18次/分
E.15~20次/分