We get molecules mainly by breaking down foods that contain starch, such as fruits, vegetables, and grains. * protein
water
amino acids
glucose

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)

The fetus at this stage is curled up, almost doubled over, so remember to consider this as you draw the fetus the correct length