Reading and responding to short comprehension questions

I’m working on a english question and need guidance to help me learn.

Some stores are testing a new checkout system that allows shoppers to use their mobile phones to scan items as they walk through stores and pay at self-service kiosks, skipping the cashiers’ lines. The new mobile checkout system is intended to reduce long lines and customer wait times in stores. What does the second sentence do?

A. It expands on the first.

B. It states an effect.

C. It contrasts with the first.

D. It gives an example.

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