D because it does not relate back to boosted brain power
The correct relative pronoun to complete this sentence.
Alchemists, _____ wanted to transform base metals into gold, were also among the first people to conduct laboratory experiments is option D. WHO
It is a non-defining realtive clause. Non-defining realtive clauses add extra information to a sentence by defining the noun. That can be used as a replacement of which or who in defining relative clauses. But it is not correct to use THAT to replace shich /who in non defining realtive caluses
"Of" is a preposition in the phrase "Of studying" and "until" is another, as well as "to" in the phrase "to college" so there are 3 in that sentence.
Instead of "his, " use "its"
Im not sure though
