Mr. Green didn’t understand ________ made his daughter so absent-minded this morning.
| A．how that was | B．what was it |
| C．why it was that | D．what it was that |
Is oxygen the only gas _______ helps fire burn?
| A．that | B．/ | C．which | D．it |
During the days ________, he worked as a servant at the Browns.
| A．followed | B．following | C．to follow | D．that followed |
The number of the people who _______ cars _______ increasing.
| A．owns; are | B．owns; is | C．own; is | D．own; are |
I shall never forget those years _______ I lived on the farm with
the farmers, _______ has a great effect on my life.
| A．when; who | B．that; which | C．which; that | D．when; which |
--- Did you ask the guard _______ happened?
--- Yes, he told me all _______ he knew.
| A．what; that | B．what; what | C．which; which | D．that; that |