Fusion, the process through which the sun produces heat and light, has

The original sentence describes fusion as a "process" studied by scientists. The
underlined portion of the sentence correctly ends with the word "scientists." This is
necessary because the non-underlined portion of the sentence, beginning "some
of whom . . .," is a long modifier that describes what some of those scientists have
attempted to do. Modifiers describing nouns must be adjacent to the nouns that
they describe.
• (A) CORRECT. This choice is correct as it repeats the original sentence.
• (B) This choice incorrectly shortens the modifier that describes fusion to "the
heat and light produced by the sun." This distorts the meaning of the sentence
by incorrectly stating that fusion is the "heat and light" produced by the sun. In
fact, fusion is the "process" used by the sun to produce heat and light; fusion is
not the "heat and light" itself. This is made clear by the use of the word
"process" in the non-underlined portion of the sentence in the phrase "to mimic
the process in their laboratories."
• (C) This choice describes fusion as "the process through which heat and light
are produced by the sun." The use of the doubly passive construction "through
which . . . are produced by" produces an unnecessarily wordy modifier.
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Though a passive construction may be correct, a more active construction is
preferable if it is provided.
• (D) In moving the word "scientists" from the end of the opening clause to the
beginning, this choice creates a misplaced modifier. The non-underlined
portion of the sentence that begins "some of whom . . ." is a modifier
describing the scientists; this modifier must be placed immediately adjacent to
the noun that it modifies ("scientists"). However, in this choice this modifier is
incorrectly placed adjacent to "heat and light."
• (E) The last word of this choice, "and," creates two independent clauses:
"Scientists have studied fusion . . ." and "some of whom have attempted . . ."
The phrase "some of whom" can only be used if it is placed immediately
adjacent to its antecedent ("scientists."). A better choice would have been
"some of them" since the pronoun "them" (unlike "whom") does not need to be
placed immediately adjacent to its antecedent ("Scientists have studied . . .
and some of them have attempted . . .").