Question

Put the verbs in brackets into the infinitive.

I heard him ... talk.
Harry felt something ... run.

Answer 1

Это структура сложного дополнения (complex object ),с данными предложениями возможны два варианта.Первый показывает однократность происходящего.
I heard him talk.
Harry felt something run.
Второе-продолжительность действия
I heard him talking.
Harry felt something running.

Answer 2

I heard him talking.
Harry felt something running.