Last night, the temperature was colder than tonight. this could be because

a-there are clouds in the sky tonight to trap heat
b-there were clouds in the sky last night that reflected heat
c-the humidity level was higher last night
d-the air is drier tonight

The correct answer is option A.

The temperature on a cloudy day is more as compared to the the temperature on the normal day or a non cloudy day. Clouds trap the heat that is being absorbed by the earth surface.

At day the heat from the sun is absorbed by the earth's surface and this heat is radiated during night and due to this fact the night is colder.

But if there are clouds in the sky it does not allows the heat to escape from the surface of the earth at night. They trap heat.