The time required for one cycle, a complete motion that returns to its starting point, is called the

The time required for one cycle, a complete motion that returns to its starting point, is called the period .

Explanation:

Any motion that repeats at regular time intervals is called periodic motion. This kind a motion has some characteristics like the period. Other important characteristic is the frequency, which is the number of complete cycles in a given time, that is, the inverse of the period.

cell differentiation  is how generic embryonic  cells  become specialized  cells. this occurs  through a process called gene expression. gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a  cell  functions.

explanation: