用have has there is there are 适当形似填空：How many ducks ( ) on the river

用have has there is there are 适当形似填空：How many ducks ( ) on the river
用have has there is there are 适当形似填空：How many ducks ( ) on the river

用have has there is there are 适当形似填空：How many ducks ( ) on the river
How many ducks (are there ) on the river?
河里有多少鸭子呢?

are there