It was our first day back at school. We on holiday.

were

are

had been

were

Объяснение:

It was our first day back at school. We were on holiday.

It was our first day back at school. We were on holiday

Объяснение:

WE -мы , мы это множесттвиное число HAD BEEN явно уже не подходит по правилу , ARE не подходит потому что снова же это правило времен , и из этого исходя выбираем WERE