Fat has two components, glycerol and fatty acids. They enter common pathway of respiration as
Glycerol + ATP → Glycerol-3-phosphate + ADP
Glycerol-3-phosphate is then converted to dihydroxyacetone phosphate by enzyme glycerol phosphate dehydrogenase which enters into glycolysis.
Glycerol-3-phosphate + NAD+ → Dihydroxyacetone phosphate + NADH + H+
The fatty acids are converted to acetyl coenzyme A by beta oxidation. The acetyl coenzyme A enters into Krebs cycle and oxidised to carbon dioxide and water.
Thus, the correct answer is option B.