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 reduces 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.