The answer is; B
Sometimes winds carry the sand of the beaches causing erosion. The fences act as breakers of this wind erosion. As wind tries to carry the sand, they encounter the fence and 'break'. Therefore, the sand is deposited along the fence forming a sand dune. These dunes also form protection from storm surges.
In biology, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of residues that form temporary bonds with the substrate (binding site) and residues that catalyse a reaction of that substrate (catalytic site).
Answer:
Cell membranes are selectively permeable which means it allow certain molecules to move across it into and out of the cell. Cells need to be able to transport these substances to live and grow.
Transport of ions, water maintains the osmotic pressure of the cell. Transport of sugars like glucose is necessary to generate energy for the metabolic activities of the cell. Gases like CO2 are waste products of metabolic reaction which are removed by the cell through the cell membrane. Amino acids are required to make proteins.
Transport across cell can occur through active and passive transport and transport of these substance are necessary for a cell to live and function properly.
The answer is C. The brain stem controls blood circulation.