Several weeks had gone by _______ we realized the painting was missing.
| A．as | B．since |
C．before | D．when |
Many experts believe that teachers' development is ______ the key to better education lies.
| A．that | B．what |
| C．where | D．which |
Great honors will be given to ______ have successfully rescued the victims of the earthquake.
| A．those who | B．whoever |
| C．who | D．whom |
The biggest surprise for John was ______ he was chosen as team captain.
| A．when | B．what |
| C．which | D．whether |
The conference aims to develop business and let people think about ______ they can have a positive influence on the Earth.
| A．why | B．that |
| C．what | D．how |
It makes his life quite different ______ he has received higher education abroad.
| A．that | B．which |
| C．what | D．how |