听力原文:There is no need to purchase fuel to operate a solar heating system because sunshine is free to everyone. (25)
A.
Though sunshine is free, we still need to purchase fuel to operate a solar heating system.
B.
We need to purchase a solar system before we can use the sunshine.
C.
If we want to use sunshine for the solar heating system, we must buy fuel first.
D.
It's not necessary to buy fuel to run a solar heating system.