What have you done______ the nuts?—We’ve given them to Polly. [ ]

Is it your brother playing football outside? — It ________ be him. He is helping mother with dishes now.

Is the blue ruler _______? —No. _______ ruler is red.

There used to ________ a clean river in the village, but now it’s dirty.

Is this kite ________? –No, it’s mine. It’s made by ________.