In a multicellular organism, nerve cells are different from muscle cells because
a. each cell type has a unique set of transcription factors and repressors, so it expresses a specific set of genes.
b. each type of cell within a multicellular organism contains a different set of genes.
c. random events within each cell regulate the expression of genes and result in different genes being expressed in different cells.
d. cells gain and lose different genes during embryonic development, so each cell in an adult only has some genes from the original set,
Answer: a. each cell type has a unique set of transcription factors and repressors, so it expresses a specific set of genes.