____is certain is ___prevention is more important than treatment .
A．It;that  |
B．What;that | C．As;what | D．What;what |
In _____world, where computers rule our work and life, online searches have become _____necessity.
| A．a, a | B．a, the | C．the, a | D．the, / |
My boss hates interruptions,when he is trying to work.
| A．occasionally | B．generally | C．specially | D．especially |
Mother always tells me to believe in myself, ____ that nothing is too difficult to a willing heart.
| A．to say | B．saying | C．said | D．having said |
In order to understand the____ of the animal, she spent many years recording its daily activities.
| A．performance | B．deed | C．behavior | D．personality |
Only after the woman had her own child ___ how difficult it was to be a mother.
| A．she realized | B．had she realized | C．she had realized | D．did she realize |