--Shall Mary come and play computer games?
--No,__________ she has finished her homework.
| A．when | B．if | C．unless | D．once |
--- John is said to have written two books last year.
一Yes, so he＿＿．They are both about the Second World War.
| A．is | B．does |
| C．has | D．did |
Vitamin D gets produced when animals are exposed to direct sunlight, for＿reason, it
is always advisable to give them chances to spend time in the sun.
| A．whose | B．that |
| C．which | D．its |
In the middle of February, the weather＿＿favorable for work, the workers began to repair and secure the dam of the river.
| A．was | B．being |
| C．would be | D．to be |
The local guide told the explorers that ropes and knives were＿＿wanted to go into the inner part of the mountain must take along.
| A．that whoever | B．what who |
| C．what whoever | D．that who |
In many cities of China, if an ambulance is＿＿in a traffic jam, police will respond to the emergency.
| A．held up | B．held back |
| C．held down | D．held out |