What is the role of these bacteria in the nitrogen cycle?
to absorb nitrogen-containing compounds from the soil
to release free nitrogen into the atmosphere
to break down nitrogen-containing compounds in dead
organisms
to convert free nitrogen into usable nitrogen

answer:

h

explanation:

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.