The well was found __________ when we go

在电梯出现超速状态时，（）首先动作而带动其他装置使电梯立即制停。

A、安全钳

B、限速器

C、缓冲器

D、选层器

用动词的适当时态填空。

1. —Oh, what a beautiful song!

    —Who ________ this song? (sing)

2. —Where ________we________ (meet)?

    —Let's meet outside the park gate.

3.—Where is Tom?

   —He ________ (go) to the post office. I think he ________ (come) back soon.

4.Your brother _________ ( study) it since he was ten years old.

5.How long ________ you _________ (do) your homework so far?

《固定式压力容器安全技术监察规程》规定安全阀一般每年至少校验一次。

卵巢表面覆盖有

A．浆膜
B．生发上皮
C．卵巢白膜
D．卵巢皮质
E．结缔组织

转运货物必须在6个月内办理海关有关手续才能运出境