Answer the following question given this paragraph: 

Your body needs proteins to create muscles, regulate chemical reactions, transport oxygen, and perform other important tasks in your body. But how are these proteins built? They are made up of units called amino acids. Just like there are only a few types of blocks in a set, there are a limited number of amino acids. But there are many different ways in which they can be combined.


Q: What is needed to create muscles, regulate chemical reactions, and transport oxygen?

 Choices:

- cytoplasm

- lipids

- enzymes

- proteins

A:
proteins
