Most bacteria are surrounded by a rigid protective structure called the . •cell wall
•cell membrane
•flagellum
•protein coat

Most bacteria are surrounded by a rigid protective structure called the cell wall.

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