_____, he cannot solve the word puzzle.
| A．Hard although he tried | B．He tried hard although |
| C．However hard he tried | D．As he tried hard |
—Are you ready for Spain?
—Yes，I want the girls to experience that ________ they are young.
| A．while | B．until | C．if | D．before |
We'll have a picnic in the park this Sunday ________ it rains or it's very cold.
| A．since | B．if | C．unless | D．until |
I'm sorry you've been waiting so long，but it'll still be some time ________ Brian gets back.
| A．before | B．since | C．till | D．after |
—Did you return Fred's call?
—I didn't need to ________ I'll see him tomorrow.
| A．though | B．unless | C．when | D．because |
A small car is big enough for a family of three ________ you need more space for baggage.
| A．once | B．because | C．if | D．unless |