问题
填空题
补全对话。
1. —What's this? 
—It's ________.
2. —Is this a pencil?
—No, it ________. It's a ________. 
3. —Is it a ________? 
—Yes, it is.
4. —Is it a bag?
—No, it isn't. It's ________. 
答案
1. a ruler 2. isn't, watch 3. baseball 4. a book/dictionary