The vacuum tube,invented near the beginning of our century,gave us the use of radio waves,an energy source never before（ ）,and later opened the road for television.

单选题

The atmospheric pressure on a standard day at sea level will force a column of mercury up into a vacuum tube _______ inches.

答案解析

单选题

The vacuum tube,invented near the beginning of our century,gave us the use of radio waves,an energy source never before（ ）,and later opened the road for television.

答案解析

单选题

Move the tube to make the inner connection tight.

答案解析

单选题

All three bracket holes must align with the fuel tube.

答案解析

单选题

The primary purpose of the glass envelope of an x-ray tube is to_____.

答案解析