Allosteric enzyme regulation is usually associated with

a) feedback inhibition
b) activating activity
c) an enzyme with more than one subunit
d) the need for cofactors

The correct answer is: C) an enzyme with more than one subunit

An allosteric regulation of an enzyme refers to the binding of effector molecules at a site other than the enzyme's active site. That site is called the allosteric site or regulatory site. When the regulator (effector molecule) binds enzyme usually goes through conformational change. When the activity of the enzyme is reduced, we call effector molecule inhibitor, otherwise it is activator.

Allosteric enzymes usually have multiple active sites located on different protein subunits, but when one effector molecule binds all sites on different subunits are changed .

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.