Which group of words in the following sentence is a dependent clause?

Yesterday morning, Sam slept late because there
is no school on holidays.
A. Yesterday morning
B. Sam slept late
C. because there is no school on holidays
D. Sam slept late because there is no school on holidays
is it c?

Great! C is right.

Yes, you are correct. Option C, "because there is no school on holidays," is the dependent clause in the sentence.