My laptop computer, _______ I can’t go on with my work, broke down the other day.
| A．for which | B．which | C．without it | D．without which |
Bad habits, ____formed, are difficult, and sometimes impossible to shake off.
| A．once | B．before | C．until | D．unless |
Only when you leave your parents for college education _______ how much you love them.
| A．do you realize | B．you realize | C．you will realize | D．will you realize |
The cause he had devoted himself to _______ a perfect success.
| A．proving | B．proved | C．was proved | D．has been proved |
Many experts believe that teachers’ development is _____ the key to better education lies.
| A．that | B．what | C．where | D．which |
Evidence has been piled up_____drinking water after getting up in the morning contributes to one’s health.
| A．what | B．which | C．if | D．that |