Ответ:
was - ед. число утверждение (he, she, it, I)
He/she/it was at home yesterday - он/она/оно был дома вчера
were - мн. число (we, you даже если you - в единственном, they)
We/you/they were at home yesterday - Мы, ты, Вы, Они был(и) дома вчера.
was not и were not - отрицание, употребление такое же:
was not - ед. число отрицание (he, she, it, I)
He/she/it was not at home yesterday - он/она/оно не был(а/о) дома вчера
were not - мн. число (we, you даже если you - в единственном, they)
We/you/they were not at home yesterday - Мы, ты, Вы, Они не был(и) дома вчера.
1) - was
2) was
3) Was
4) was not
5) were
6) Were
7) were not
8) were
9) were
10) was (если стоит I)