胶黏剂的定义是什么？
参考答案：
胶黏剂是一类通过黏附作用而使被粘物体结合在一起的物质。
Read and choose.（读句子，根据内容选择正确的句子）
1. 如果你想说”，应该说：___________[ ]
A. They have a picnic.
B. They are having a picnic.
2. 如果你想问“John正在做什么？：___________ [ ]
A. What is John doing?
B. What does John do?
3. 如果你想说”，应该说：__________[ ]
A. She is coming.
B. She is running to us.
我国邮政物流于（）年正式在全国开办。
A.2000
B.2001
C.2003
D.2004
