The correct answer is option 1: Liver. The liver is responsible for synthesizing cholesterol in the human body. Cholesterol is a waxy substance that is needed for a variety of vital functions, such as the production of hormones, cell membranes, and vitamin D. The liver synthesizes cholesterol by converting acetyl-CoA into cholesterol through a series of enzymatic reactions known as the mevalonate pathway.

Option 2: Pancreas is incorrect. The pancreas is primarily involved in the production of enzymes that aid in digestion and the regulation of blood sugar levels.

Option 3: Spleen is incorrect. The spleen is responsible for filtering and storing blood, but it is not involved in the synthesis of cholesterol.

Option 4: Skeletal muscle is incorrect. While skeletal muscle plays a role in the movement of the body, it does not synthesize cholesterol.

Therefore, the correct answer is option 1: Liver.