今年春节期间，我国南方地区普降大雪，给人们出行带来诸多不便，生产生活受到很大影响

The first recorded use of natural gas to light street lamps it was in the town of Frederick, New York, in 1825.

A．was

B．is

C．it is

D．were

用 come about, happen, take place, break out, occur 的正确形式填空.

① I was out of town at the time, .so I don't know exactly how it _________ .  

②The meeting _________ at 8:00 as planned.  

③It ________  to rain that morning.  

④A fire  ________     in the hotel last night.  

⑤It suddenly ________ to me that I had left my key in the office.

PDH设计规范中我国中级假设参考数字通道长度为2500公里。

在卸钻头时，应用什么松扣，什么卸扣？

教学目标