At last the people ... outside were invited in A) which was waiting B) what were waiting C) which were waiting D) who were waiting E) who was waiting

At last the people who were waiting outside were invited in

A) which was waiting B) what were waiting C) which were waiting D) who were waiting E) who was waiting

Правильный ответ - D, так как:

- which and what больше относятся к неодушевленным предметам

- who - к людям

Итого остается 2 варианта - D и E. Но так как в предложении стоит "people" (людИ, множественное число), подходит только до, т. к. were употребляется с мн. ч., was - только с ед. ч.