Vaccines work by priming the immune system and inducing the formation of antibodies and memory cells. When the actual virus infects the host, the host's immune system recognizes and responds to it. What feature(s) of HIV allow it to thwart this system, making a vaccine difficult

i think that it is plants

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.

a researcher conducts an experiment on the secretion of a particular hormone in mice. scientists inject mice with a substance that stimulates the production of the hormone. the scientists then test the levels of hormones produced by the mice. the tool used to measure the hormones consistently detects the levels at 10 points lower than the actual hormone levels in the mice. this tool makes measurements, but the measurements aren't .

explanation:

no u

you know they are heterozygous for a trait because they have it as jj or jj.