机电产品国际招标可选择的付款方式较多，但是国内招标一般不会使用( )付款方式。
A．信用证 B．现金C．电汇 D．银行托收
参考答案：A
My grandfather is very old, _______ he never stops learning.[ ]
A. than
B. though
C. but
D. unless
根据汉语提示完成对话。
Boy: Doctor, I'm too heavy.Can you help me to lose some weight?
Doctor: 1._____ (每天做早操很有必要)
Boy: 2._____ (吃很多甜食不好，是不是)?
Doctor: That's right. It's bad for you to eat too much sweet.
Boy: 3._____ (每天游泳1个小时， 行不行)?
Doctor: Yes, that's a very good exercise.
Boy: Anything else?
Doctor: Yes. 4._____ (饭前可以吃点儿水果)
1._______________________________________
2._______________________________________
3._______________________________________
4._______________________________________
