Ответ:
was / wasn't - для единственного числа
were / weren't - для множественного числа
В вопросе меняем подлежащее и сказуемое местами:
There was.... => Was there....?
There were.... => Were there...?
1 There were
2 There was
3 there were
4 Was there
5 there wasn't
6 there was
7 Was there
8 there was
9 there weren't
10 Were there
Объяснение: