Hiv is the virus that causes aids. in the mid-1990s, researchers discovered an enzyme in hiv called protease. once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. if this strategy for stopping hiv infections were successful, it would be an example of what phenomenon?

   Competitive inhibition

Explanation:  Competitive inhibition means that a chemical substance, so in this case, the drug is inserted and competes with an enzyme detected in the HIV virus. So a chemical substance, a drug, inhibits, or simply takes the active place of a detected enzyme called protease, and inhibits its effect by competing with it, so the drug substance competes with a enzyme protease for binding.

a is the answer because it just is

d - failures.

the only attempted british colony in north america before 1600 was roanoke, virginia, which was a total failure. england claimed several areas, including newfoundland, but made no sustainable attempts to colonize them before 1600.