Where do animal cells get the molecules, such as proteins, that they use for growth, repair and other life processes?
A.
The animal takes in materials from the environment, and the cells use the materials without changes.
B.
The small intestine makes them from food that the animal ingests.
C.
The lungs make them from gases the animal takes in when it breathes.
D.
The cells make them from materials the animal takes in from the environment.