The correct answer is the first one.
He describes Mrs. Miller's behavior as "unprecedented." By this, he is saying that, of all the parents he has ever known, her behavior is unusual, singular, or unique.
Quite simply, it is strange that she would allow her daughter to run around town with a strange man. Mrs. Miller's behavior is more than silly -- it is downright unheard of.
For me, the answer is letter D.
Only choice D has the technical words associated to geography. The rest of the choices contain common words that any mundane could use. But choice D talks about geology itself in the ocean which is highly influenced by drilling and mining. Knowledgeable readers would understand this because drilling and mining require workers to tap into the geological rocks deep beneath the ground which may cause a significant alteration in the oceanic geology.
I would think <span>c)both a and b are correct </span>
