Radiation fog forms at night when the skies are clear and the relative humidity
is high
a. true
b. false

A. True

Explanation:

I'm not all the way sure, so please don't hate on me. I looked it up to double check and it should be true.

                                !PLEASE NOT HATE IF IT'S WRONG!

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).