_____wants to stay in a hotel has to pay

The old man has expected to see all his children when he was in hospital, but ______ came to see him.

A．none

B．no one

C．someone

D．anyone

同温同压下，等质量的下列气体所占有的体积最大的是（　　）

A．SO₂

B．CH₄

C．CO₂

D．O₂

一条物理信道直接连接两个需要通信的数据设备，称为______通信。

4正心瓜栱（泥道栱）

SOG型燃烧器具有空气和燃料混合均匀，燃烧完全的特点。（）