What is the mass of stem cells produced in the first few days after fertilization called?

The correct answer is Morula stage.

Explanation:

Morula is the solid ball of cells formed by fertilized ovum and later forms blastula stage in the embryonic stage. This solid ball of the mass consists of 10 to 30 cells.  

It is the final stage before the formation of the blastocoel, a fluid-filled cavity. It is the initial embryonic stage where mammalian cells fate decided to become either internal or external.

Thus, the  correct answer is Morula stage.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.

well for one plants are always the producer, so a is the answer. a wolf is more of the consumer(predator) and the deer is the prey so i know those two are out of the question. also mushrooms are fungi/fungus so a is the producer.