18. I am not sure whether I can gain any profit from the investment, so I can’t make a(n) ____ promise to help you.
A. exact B. defined C. definite D. sure
<investment>
investment 投资
investigate 调查
irrigate 灌溉
irritable 激怒的
navigate 航行
castigate 惩罚
mitigate 缓和，调解，减轻
</investment>
<sure>
sure 确信
insure 保险
ensure 确保
</sure>
define 限定，下定义
final 结束的
refine 提纯
finance 财政，资金
