APPEAR, HAPPEN, PROVE, SEEM, TEND, TURN OUT + TO-infinitive

These verbs are followed by a to-infinitive:

I appear to have lost my keys.
I happened to be passing your house, and I saw that the door was open.
Our predictions proved to be accurate.
She seems to understand most of what we say.
The library tends to be crowded during the exam period.
The concert turned out to be much better than we had expected.