Subject-verb agreement with number, range and total

Collective nouns such as number, range and total can be troublesome in terms of subject-verb agreement. In the sentences below, decide whether the sentence needs a singular or plural verb.

1. The number of survey respondents dismally low.a) wasb) were
2. A range of dresses been designed for the fashion show.a) hasb) have
3. A number of partygoers dressing up for the occasion.a) isb) are
4. A total of 12 students chosen to go to Paris.a) wasb) were
5. The total of the company's assets staggering!a) isb) are
6. The range of ideas at the conference very inspiring.a) wasb) were
7. A number of candidates tied for first.a) hasb) have