The dog sitting at the door is waiting for its owner.

[neb090]

The dog sitting at the door is waiting for its owner.

Which of the following sentence is the original form:
1. The dog that is sitting at the door is waiting for its owner.
2. The dog that sits at the door is waiting for its owner.

 

[Skrej]

Are these your own sentences? What do you mean by "original form"?

Which of the following sentences is the original form:

You've made this very basic mistake now on several posts. You need to focus on subject-verb agreement.

 

[teechar]

#1 is the longer version of the first sentence in your post.
"(that is) sitting" - now.
"that sits" - usually.