13. A multicellular organism generally includes a wide variety of cell types. Examples in vertebrates include blood cells, neurons (cells of the nervous system), and the cells that line the digestive tract. What is the role of DNA replication and gene expression in cell differentiation?

A. Only the DNA that a cell will use is replicated, and all of the genes that it contains are always expressed.
B. Only the DNA that a cell will use is replicated, and gene expression is tightly controlled.
C. Nearly all DNA is replicated, and the omissions determine gene expression in the cell.
D. All DNA is replicated, but gene expression varies widely among cells and over time.

good luck

explanation:

i still can't find this

science-ocean floors and habitats study guide by volleyballqueen3817 a major advance in ocean-floor mapping. list four sections of the ocean floor. algae that use sunlight to produce their own food through photosynthesis. all of the feeding relationships that exist in a habitat. drying out, predators, find food.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.