their large, chemical-energy reserve their large, stored-electric potential the complexity of their folded structure the wide variety of elements they include
I gave my students this multiple choice question: Which property of proteins best allows them to perform an enormously diverse range of functions?

Only one answer is correct among these 4 choices:
- their large, chemical-energy reserve
- their large, stored-electric potential
- the complexity of their folded structure
- the wide variety of elements they include

Could you tell me which one is correct?

the complexity of their folded structure