9. What is this for?
这是什么钱?
还能这样说：
What is this charge for?
What is this amount for?
10. Keep the change.
不用找钱了。
还能这样说：
You don't need to give me the change.
Never mind the change.
应用解析：
a change for the better/worse 现有的或曾有过的事物的改善或变坏;
change hands 归另一个人所有，转手;
change one's spots 违反本性或做违反本性的事，改变本性
11. Would you like to sign for it?
你是签名记账吗?
还能这样说：
Will you choose to sign for it?
Would you like to pay the bill by signing here?
应用解析：
at the sign of 当有……的迹象;
bear the sign of the times 带有时代的特征;
put the Indian sign on 施以魔法;
sign language 手势语，手语;
sign on the dotted line 签署文件等
12. Can I use this voucher to pay the bill?
我可以用这张餐券付账吗?
还能这样说：
May I use this meal ticket to pick up the tab?
Would you mind my using this meal coupon to foot the bill?
应用解析：
tax bill 税法;
acceptance bill 承兑票据;手续费