If air were a better conductor than it is, at nighttime the Earth would be?

a. considerably colder.

1.If air were a better conductor. Energy will be lost quickly during the night, a.colder

2.d.radiation, more precisely infrared radiation.

Look what I found. Check out this link I googled.

1.) a (for sure)

2.) d (probably because silver coated glass is essentially a mirror which would reflect radiation a.k.a no absorption)

Sounds like someone is taking a heat transfer class… good luck with that.