13. Heavy enquiries witness the quality of our products.
大量询盘证明我们产品质量过硬。
还能这样说：
Heavy enquiries can prove that we have good quality.
A lot of enquiries bore witness to the quality of our products.
应用解析：
bear witness to sth. 证明某事物，为某事作证；
eye-witness 目击者；
a witness against sb. 对某人不利的证人；
witness to sth. 在法庭等上作证

14. We've already cut down our prices to cost level.
我们已经将价格降到成本费的水平了。
还能这样说：
The price we give you is the cost level.
This is already our cost price. We can't reduce it any more.
应用解析：
hair cut 理发；
power cut 停电；
a cut above 高人一等的；
cut across sth. 与通常的分类不符；
cut and run 急忙逃跑；
cut no ice 不起作用

15. I wish that this business will bring benefit to both of us.
希望这笔生意对我们双方都会带来好处。
还能这样说：
I hope that both of us will benefit from the business.
I desire that this business will do good to both of us.
应用解析：
for one's benefit 以对某人进行指引、指导；
give sb. the benefit of the doubt 因证据不足而承认某人无罪；
benefit from sth. 从某物中利益；
be of benefit to 对……有益

16. You may trust me that any money spent now will bring you big profits in future.
请您相信我，今天投入的资金以后会为您带来巨大的利润。
还能这样说：
You can believe in me, the money you spent today will make you gain a lot in the future.
You can have faith in me that if today's little money doesn't go out; tomorrow's great money doesn't come in.
应用解析：
have big ideas 想要做大事的；
get too big for one's boots 自大，自负；
a big cheese 要人，大亨；
big deal 重要的人；
a big fish in a little pond 小地方的大人物