I did not wait for him to speak, but at once began to explain my presence.

Spreading the plans on the floor, he began to explain them to her.

I can't begin to explain what that will mean to me.

They looked at him and he began to explain about his models.

I sat down on a boulder and began to explain to him what this was all about.

Knew it in a way he could not begin to explain.

Possibly not; but this doesn't begin to explain why they killed.

Looking back into the cave toward her, I began to explain.

Don't ask me what was going through my head, I couldn't begin to explain.

That wasn't even half of it, but she couldn't begin to explain.