Have you ever seen any trees ________ leaves were black because of the polluted air?
| A．whose | B．that |
| C．which | D．who |
I like ____ in the autumn when the weather is clear and bright.
| A．this | B．that | C．it | D．one |
It was at four o'clock in the afternoon ____ he and his grandpa reached the museum in Guanghan.
| A．while | B．that | C．when | D．as |
I consider____ my duty to help you．
| A．it | B．this | C．that | D．its |
Is＿possible to fly to the moon in a spaceship?
| A．now | B．man | C．that | D．it |
Is＿necessary to tell his father everything?
| A．it | B．that | C．what | D．he |