The answer is D . Would you like me to explain ?
C. It requires active transport because the use of energy is necessary, the natural and opposite flow to this, would be from high to low concentration that requires little to no energy (i.e passive diffusion).
Catalysts can speed chemical reactions by lowering the activation energy
Skin and Integumentary system protects by forming a selective barrier.
<u>Explanation</u>:
Multicellular organisms unlike unicellular organism have a variety of systems each having a different function. The body of multicellular organisms is covered with epidermis or skin which is known as largest organ of the body. The skin consists of many sensory receptors and protects by enclosing muscles and other body tissues. While Integumentary system is made with skin and its various appendages like hair, feathers, nails etc. with receptors and secretary pores and protects the body from pain.
