Proteins in a membrane are .
a. peripheral if they are on the inside surface held in place by the cytoskeleton.
b. integral if they are embedded in the membrane and protrude from either surfaces of the bilayer.
c. Both answer choices are true.
d. Neither answer choice is true.

Proteins in a membrane are C. Both answer choice is true.

Explanation:

Membranes have different types of proteins. Peripheral proteins are the ones that are placed on the inside suface held in place by the cytoskeleton. Integral proteins are the ones that are embedded in the membrane and protrude from either surfaces of the bilayer. These integral proteins also can be carrier proteins, which facilitate passage of molecules through the membrane ; enzymatic proteins, whichcatalyze a specific reaction  or they can recognize pathogens, baing cell recognition proteins. In the membrane we can find aquaporins too, which are membrane channel proteins that enable water to cross a membrane.

c. Both answer choices are true.

Explanation:

Peripheral proteins and integral proteins are a type of membrane proteins that play a vital role in signal transduction, enzyme activity, cell adhesion and transportation of molecules.

Peripheral proteins are attached to the lipid bilayer temporarily at either one side of the lipid bilayer and can be easily dissociated from the lipid bilayer when treated with polar solution. It plays an important role in transportation,  maintaining the shape of the cell as well as signal transduction.

Integral proteins span the two sides of the lipid bilayer and are attached to it permanently, it can only be detached by the treatment with non polar solutions. It plays an important role in cell adhesion and transportation.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.