Is Lily good at singing? —Yes , she is．We often hear her_______ in the next room．

Go and ask Mr Green for help.—But I don’t know ______.

Is this __________ ruler? —No, it’s my ruler. __________ is over there.

Must we finish all the exercises today? — No, you ________.You can finish them within two days.

The building ______ stone and each stone ______ more than two tons (吨).[ ]