In all furnace cabinet configurations, the return air :

In all furnace cabinet configurations, the return air
 
  A) enters at the heat exchanger end and exits the fan housing end of the furnace
  B) enters at the fan housing end and exits the heat exchanger end of the furnace
  C) and combustion air enter the furnace through the same opening
  D) enters as combustion air, travels through the heat exchanger, and exits the fan end of the furnace

 Q. 2

A dent or crater in a pipe can be a hiding place for _____.
 
  a. excess flux
  b. oxidation
  c. incorrect filler metal
  d. thick copper deposits