It wasn't clear what she meant.

Source: Tatoeba

I'm not really sure what Tom meant.

Source: Tatoeba

Turn up the radio. I can't hear it.

Source: Tatoeba

I never know what to say to people who have absolutely no grasp of the basic facts and are too ignorant to realise it.

Source: Tatoeba

I have no idea of what's going on in there.

Source: Tatoeba

My father is so old that he is hard of hearing.

Source: Tatoeba

No matter how much I consider it I do not understand.

Source: Tatoeba

Tom doesn't know whether Mary likes him or not.

Source: Tatoeba

"What exactly does this do?" "I'm not sure."

Source: Tatoeba

Tom is still uncertain about whether to go to college or not.

Source: Tatoeba

I'm not sure what's going on.

Source: Tatoeba