Answer:
B
Explanation:
It represents the greatest amount of cell differentiation for the newly formed organism.
Here all the organs and system get initiation and cell differentiate to form various organs.
Primary reinforcers have distinctive reinforcing qualities; not learned. In addition, secondary reinforcers has no inherent value and only has reinforcing qualities when linked with a primary reinforcers. The positive reinforcement is a desirable stimulus is added to increase behavior while negative reinforcement is an undesirable stimulus is removed to increase behavior.
The phase when the moon is not visible is in the last quarter phase