20. —Why was __ you lost all your keys？
—It was because of my carelessness.
| A．that | B．what | C．it that | D．One |
I like getting up very early in summer. The morning air is so good ______.
| A．to be breathed | B．to breathe |
| C．breathing | D．being breathed |
The fire made _____ difficult to rescue the people trapped under the ruins in the earthquake.
| A．/ | B．this | C．that | D．it |
The mother waved to her daughter until the train .
| A．out of sight | B．got out of sight |
| C．caught sight | D．lost sight |
He hurried to the station only that the train had left.
| A．to find | B．finding | C．found | D．to have found |
It was Asimov was eleven years old his talent for writing became obvious.
| A．that, when | B．When, that |
| C．when, when | D．when, which |