Which of the following is true regarding membrane proteins?
a. all peripheral membrane proteins contact the lipid bilayer by covalent attachment to the hydrophilic head groups on membrane lipids
b. beta strands can assemble into a membrane-spanning barrel structure.
c. lipid-anchored membrane proteins always face the cell exterior.
d. a protein with six hydrophobic helices is most likely a lipid-anchored membrane protein .

Option C. Lipid-anchored membrane proteins always face the cell exterior.

Explanation:

Lipid-anchored proteins are proteins located on the surface of the cell membrane which are attached to lipid and embedded within the cell membrane. The lipid-anchored proteins assume a place in the bilayer structure of the membrane.

i believe you meant to say air rather than hair so the answer is below ")

the dead sea, the lowest place on earth at 430 metres (1,410 ft) below sea level, has a correspondingly high typical atmospheric pressure of 1065 hpa.

frogs. the lower the ph the higher the acid content. frogs have the highest tolerance in this scenario.