Which of the following is considered a big molecule?

Fats are considered big molecules because they are composed of larger structural units that include glycerol and three fatty acid chains. This structure categorizes fats as triglycerides, which are significantly larger than single molecules of sugar or individual amino acids.

In contrast, sugar molecules are typically smaller carbohydrates, and amino acids are the building blocks of proteins, each being relatively small on their own. Fatty acids, while part of the larger fat structure, are also single-chain molecules that do not qualify as large complex structures by themselves. Hence, fats, with their multiple components come together to form a more extensive and complex molecular structure, making them the correct answer in terms of size.