. During development, some cells become liver cells, somet ells and some become muscle cells. This process is called

Cellular differentiation.

Explanation:

Cellular differentiation is the process in which a cell changes from one call type to another. Usually, the cell changes to a more specialized type. Differentiation of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types.

name and explain one of the event that occurs during meiosis that increases the variation in offspring even more than simple reproduction?

that is wrong, its not thymus.