Tom kept quiet about the accident　　　 lose his job.

A．so not as to

B．so as not to

C．so as to not

D．not so as to

表面微裂纹是由于晶体缺陷或外力作用而产生，微裂纹同样会强烈地影响表面性质，对于脆性材料的强度这种影响尤为重要，微裂纹长度（），断裂强度（）。

A.越长；越低

B.越长；越高

C.越短；越低

D.越长；不变