Complex sentences with predicative clauses

The connecting verbs that can be connected with predicative clauses are be, look, seem, sound, apparent and so on.

Example:

China is no longer the China it used to be. Today's China is not the China it used to be.

The question remains where they can help us. The question is whether they can help us.

At that time, I couldn't seem to think of the right words. I couldn't seem to think of a suitable word at that time. ?

B-guided predicative clause as, if/though

For example:

He looks the same as he did ten years ago. He still looks the same as ten years ago.

It sounds as if someone is knocking at the door. Does it sound like someone is knocking at the door?

C-guided predicative clauses because, why

When the subject clause led by what or noun reason is the subject, the predicative clause behind it should be led by that, not because.

For example:

That's because he doesn't understand me. That's because he doesn't understand me.