1. This is my ruler. (改为复数形式) ____ ______ my____ . 2. Are those your sisters? (改为单数形式) _____ ______your____? 3. He is my grandfather. (改为一般疑问句并作肯定回答) _______ ______ ____grandfather? _______ ______ ____. 4. That is his friend. (改为否定句) _______ ______ ____friend.