2. Which is more important for a 
     wet suit to be effective?

Answer: B- The fit of the wet suit

Yes. Fit is the key. By fitting closely and evenly
over the skin, only a small layer of water gets in
between the neoprene and your skin. Your body
can easily heat this thin layer of water. Remember
that your skin would ordinarily be transferring heat
directly to the surrounding air and water. Heat and
cold do not easily pass through the neoprene because
it is an effective insulator. A poor fitting vest or wet suit
that allows cool water to wash through would not
be as effective. An ordinary t-shirt is, of course,
of little benefit because it does not create an insulating
barrier necessary to contain body heat.