Of these gases, which has the fastest-moving molecules (on average) at a given temperature?

I believe we are choosing between HBr, NO2, and C2H6.

The molar masses of these compound are:

Molar mass of HBr = 80.9119 
Molar mass of NO2 = 46.005 
Molar mass of C2H6 = 30.0694 

The speed of the molecule actually is inversely proportional to its molar mass. Hence, the lighter the molecule, the faster it moves.

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

i think? ?