SDH的带宽利用率比PDH高。
参考答案:错
Do you know ______ in Japan? [ ]
A. when nuclear (核) accidents happened
B. when did nuclear accidents happen
C. when nuclear accidents happen
D. when do nuclear accidents happen
在凸轮机构中,不属于常见凸轮形状的是()。
(A)盘状
(B)圆柱
(C)圆锥
(D)梯形