Which sentence includes a dependent clause?

A. The boy received a dog named rover for his birthday
B. They gave sandwiches to the children on paper plates
C. When looking out the window they saw the first leaf fall
D. On the way to the store, Nicole saw a lost cat

C. When looking out the window they saw the first leaf fall

The sentence that includes a dependent clause is C. "When looking out the window, they saw the first leaf fall."

To identify the sentence that includes a dependent clause, let's first review what a dependent clause is. A dependent clause is a group of words that contains a subject and a verb but cannot stand alone as a complete sentence because it does not express a complete thought.

Now, let's analyze the options given:

A. "The boy received a dog named Rover for his birthday." - This sentence consists of an independent clause (The boy received a dog named Rover for his birthday) that can stand alone as a complete sentence. There is no dependent clause here.

B. "They gave sandwiches to the children on paper plates." - This sentence also consists of an independent clause (They gave sandwiches to the children on paper plates) that can stand alone as a complete sentence. There is no dependent clause here.

C. "When looking out the window, they saw the first leaf fall." - This sentence includes a dependent clause (When looking out the window) because it cannot stand alone as a complete sentence. The dependent clause is followed by an independent clause (they saw the first leaf fall).

D. "On the way to the store, Nicole saw a lost cat." - This sentence also includes a dependent clause (On the way to the store) because it cannot stand alone as a complete sentence. The dependent clause is followed by an independent clause (Nicole saw a lost cat).

Therefore, the sentence that includes a dependent clause is option C: "When looking out the window, they saw the first leaf fall."