Which statement is true about cell differentiation?
a. it happens in all cells.
b. it causes cells to change and specialize.
c. it produces identical cells.
d. it happens during cell division.

B.It causes cells to change and specialize.

Explanation:

In the cellular differentiation  a cell changes from one cell type to another. Generally, the cell changes to a more specialized type. Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types forming a complete organism. Cellular differentiation occurs through gene expression. In this process cells become specialized in order to perform different functions.

For example generic embryonic cells become blood cells  and nerve cells.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)