There are или There is
1. a piano in my room.
2. a teacher in the classroom.
3. many toys in the box.

ответ:1)There is,2)there is,3)there are

Объяснение:

1. There is

2. There is

3. There are

Объяснение:

is с единственным числом (a piano; a teacher)

are со множественным числом (many toys)