39. Fructose in the diet or fructose from sucrose in the diet can be a source of calories for fat synthesis in the liver because: (A) ketoses are fattening. (B) fructose enters glycolysis after the primary regulation point, phosphofrutokinase-1 (PFK-1). (C) fructose provides a net of four ATP from glycolysis. (D) fructose enters the branch of glycolysis that forms fat. (E) glycerol (the "backbone" of triacylglycerols) comes specifically from fructose.