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 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
sure 确信
insure 保险
ensure 确保
define 限定，下定义
final 结束的
refine 提纯
finance 财政，资金
