單項(xiàng)選擇題對(duì)100個(gè)某種產(chǎn)品進(jìn)行壽命測(cè)試,在t=100h前磨牙失效。100~105有1個(gè)失效,失效率為()

A.0.1%/h
B.0.2%/h
C.0.4%/h
D.0.8%/h