Cell membranes serve as barriers and gatekeepers. They are semi-permeable, which means that some molecules can diffuse across the lipid bilayer but others cannot.
Answer:
part A is the answer
Explanation:
The tympanic cavity is an air chamber; it contains a chain of movable bones which transmit the vibrations of the tympanic membrane across the cavity to the middle ear.
BioSafety Level (BSL) 3 labs,
perform work with indigenous or exotic agents that may cause serious or
potentially lethal diseases through the inhalation exposure. Biological Safety
Levels (BSL) are a sets of protections assigned to the activities that occur in
specific biological laboratories. BSL protects laboratory workers, the
surrounding environment and also the community.
