Can a complete sentence have more than one subject e.g,.....?

Question

mary went shopping and bumped into sally who was on her way to pick her children up from school?

Answer 1

"Mary went shopping and bumped into Sally, who was on her way to pick her children up from school."

This sentence is correct.  However, your question is about having more than one subject.  This sentence has only one, Mary.  Sally isn't another subject; she's the direct object of the verb "bumped into" (in other words, she is the object that receives the action of being bumped into).

A sentence can, however, also have a compound subject.  In order for this sentence to have more than one subject, you would need to add another person (or thing, even) to the simple subject "Mary".  For instance, "Mary and Martha went shopping and bumped into Sally, who was on her way to pick her children up from school."  Mary and Martha comprise the compound subject.

Answer 2

It's a complex-compound sentence. "Mary went shopping" and "(Mary) bumped into Sally" are independent clauses. "who was on her way to pick up her children from school" is a dependent clause that modifies Sally.

Answer 3

No.

Let me demonstrate:

Mary (subject) went shopping and bumped (verb) into Sally (direct object) who was on her way to pick her children up (object of the verb) from school (object of the preposition).

It's really impossible unless it is combined by conjunctions.

For example:

Sentence #1: Mary went shopping.

Sentence #2: Sally was on her way to pick her children up.

Two sentences made into one sentence:

Mary went shopping (while) Sally was on her way to pick her children up.

The word enclosed in parenthesis is the conjunction which combines the two sentences.

:-)