. —Why are you so frightened—I saw two dark _______ enter the building.

I must apologize for what my son didyesterday.—Childrenare children.

I _______ meeting Jack today because I am still angry with him.—Come on， Mary. You are good friends.

______ to be old enough to live alone, Mary was sent abroad to study by her parents[ ]

If there __________ no buying and selling of animals , there __________ no killing .