1. What would have happened, ______ as far as the river bank
A. Bob had walked farther B. if Bob should walk farther
C. had Bob walked farther D. if Bob walked farther
2. _______ we’ll go camping tomorrow depends on the weather.
A. If B. Whether C. That D. Where
3. Economics, several courses of which I have taken thus far, ______ to be difficult but useful for almost all students.
A. prove B. proves C. have been proved D. are proved
4. Nine in ten parents said there were significant differences in their approach to educating their children compared with ______ of their parents.
A. those B. one C. both D. that
5. Experiments of this kind ______ in both the U.S. and Europe well before the Second World War.
A. have conducted B. have been conducted
C. had conducted D. had been conducted