doubtful

adj.

1. 难以预测的, 未定的
   • This is a doubtful battle.
     这是一场胜负难测的战争。
   • I'm doubtful where to go.
     该往哪里去我心中无底。
   • I feel doubtful what I ought to do.
     我不知该做什么。
2. 怀疑的, 可疑的
   • Let's try to clear up our difficult and doubtful points.
     让我们设法把难处和疑点解决一下。
   • I feel very doubtful about this.
     我对这点很怀疑。
   • I am very doubtful of that.
     我很疑心那件事。
   • It is doubtful whether it is true or not.
     这件事的真假是可疑的。