根据板厚和焊接方法的不同，对接焊缝的坡口主要有I形、Ｖ形、Ｕ形、（）等四种形式。
参考答案：X形
介词填空。
1. Happy New Year ____ you.
2. ____ Sunday morning, I will go to the zoo.
3. The boy ____ a blue coat is Zhang Hao.
4. We work hard ____ school.
5. It's time ____ supper.
6. Your birthday is ____ April 6.
7. I go home ____ 4:30 in the afternoon.
8. I have lunch ____ my family.
9. We are playing catch ____ Li Ming's ball.
10. We go to school ____ bus.
用链表表示线性表的优点是( )。
A．便于随机存取
B．花费的存储空间较顺序存储少
C．便于插入和删除操作
D．数据元素的物理顺序和逻辑顺序相同
