下列对发光二极管的叙述正确的是()
A.发光二极管的响应速度比激光器高
B.发光二极管的阀值电流低
C.发光二极管有寿命长,可靠性高,调制电路简单,成本低等优点
参考答案:C
Thanks for your invitation, but I’m so sorry I can’t go.
I need to ________ my baby at home. [ ]
A. take away
B. take off
C. take care of
D. take out of
精车铸铁应选用()牌号的硬质合金车刀