_______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.
| A．Even if | B． As far as | C．If only | D． So long as |
What would have happened ________, as far as the cliff?
| A．if Bob has walked farther | B．if Bob should walk farther |
| C．if Bob had walked farther | D．if Bob walked farther |
The 2010 Expo will take place in Shanghai, ________ many countries consider a good chance to introduce their cultures to the world.
| A．where | B．when | C．what | D．which |
The professor’s research finally proved to be ______, though he had spent a lot of money on it.
| A．priceless | B．valuable | C．worthless | D．worthwhile |
The purpose of our advertising is to _________ customers’ attention to our product.
| A．pay | B．devote | C．fix | D．draw |
____ is the ability to do the job rather than where you come from or what you are that matters.
| A．It | B．That | C．This | D．There |