23．What the boss really doubts is__________his employees will go on working in the company．
| A．that | B．weather | C．when | D．whether |
He wrote a letter________he explained what had happened in the accident.
| A．what | B．which |
| C．where | D．how |
Nowadays people are more concerned about the environment________they live.
| A．what | B．which |
| C．when | D．where |
Happiness and success often come to those________are good at recognizing their own strengths.
| A．whom | B．who |
| C．what | D．which |
Mo Yan was awarded the Nobel Prize for Literature in 2012，________ made one of the Chinese people’s longheld dreams come true.
| A．it | B．that |
| C．what | D．which |
The president of the World Bank says he has a passion for China，________he remembers starting as early as his childhood.
| A．where | B．which |
| C．what | D．when |