White Roof Vs. Black Roof on a house

[Dreebs]

Homework Statement

Your house will have a white roof, rather than the traditional black roof. A white roof reflects 90% of sunlight (its high-temperature emissivity is almost 0) but emits its own thermal radiation with almost perfect efficiency (its low-temperature emissivity is almost 1). How does that help keep your house (and your city) cool during the summer? Select one:
a. The roof is white across the entire electromagnetic spectrum, so it doesn't exchange heat via thermal radiation.
b. By reflecting away sunlight, your roof reduces the heat transferred to your house (and your city) from the sun. By emitting its own thermal radiation almost perfectly, your roof helps you house send its excess heat into the sky and space.
c. Although the roof looks white, the fact that it emits its own thermal radiation so well means that it is actually black across the entire electromagnetic spectrum. Black surfaces stay cooler in sunlight than do white surfaces.
d. The white roof is a poorer conductor of heat than a black roof, so it keeps your house cool.

Homework Equations

N/A

The Attempt at a Solution

B, The white roof reflects much of the sunlight thus reducing the amount of heat transferred to your house.

 

[haruspex]

Homework Statement

Your house will have a white roof, rather than the traditional black roof. A white roof reflects 90% of sunlight (its high-temperature emissivity is almost 0) but emits its own thermal radiation with almost perfect efficiency (its low-temperature emissivity is almost 1). How does that help keep your house (and your city) cool during the summer? Select one:
a. The roof is white across the entire electromagnetic spectrum, so it doesn't exchange heat via thermal radiation.
b. By reflecting away sunlight, your roof reduces the heat transferred to your house (and your city) from the sun. By emitting its own thermal radiation almost perfectly, your roof helps you house send its excess heat into the sky and space.
c. Although the roof looks white, the fact that it emits its own thermal radiation so well means that it is actually black across the entire electromagnetic spectrum. Black surfaces stay cooler in sunlight than do white surfaces.
d. The white roof is a poorer conductor of heat than a black roof, so it keeps your house cool.

Homework Equations

N/A

The Attempt at a Solution

B, The white roof reflects much of the sunlight thus reducing the amount of heat transferred to your house.

Yes, but the second part of the explanation provided in option b is also important.