Someone help me please. key word is clause!

The next question refers to the following passage. The sentences have been numbered to help you identify them more easily.
(1) As she was driving to visit her twin, Jayla had a strange feeling that something bad was going to happen.
(2) Meanwhile, Kayla had the same exact premonition.
(3) Worried about her sister, Kayla called Jayla's cell phone.
(4) Because she took her eyes off the road to answer the phone call, Jayla lost control of her car and crashed through the front of Kayla's house.

Which sentence features an INTRODUCTORY CLAUSE that explains why the main action happened?

a. Sentence 1
b. Sentence 2
c. Sentence 3
d. Sentence 4