Sentence Correction

The success of the program to eradicate smallpox has stimulated experts to
pursue what they had not previously considered possible -- better control, if not eradication, of the other infections such as measles and yaws.


A. what they had not previously considered possible -- better control, if not eradication, of the other infections such as
B. what they had not previously considered a possibility -- better control, if not
eradication, of such infections like
C. something they had not previously considered possible -- better control, if not eradication, of such infections as
D. something not considered a previous possibility -- better control and perhaps
eradication, of other infections such as
E. the possibility of what they had not previously considered possible -- better
control and possibly eradication of infections like


Can anyone help me out with the below question

1) What/which the subordinating conjunction in here
2) the coordinating conjunction
3) in 1 "what they had not previously considered possible " what is wrong with this

Thanks


C

Not sure how much the sentence posted has to do with the questions you specifically
asked.

IMHO
"what/which" isn't tested in the question; however, option 1 failed not because it
used "what" but because of the usage: "of the other infections such as"

IMHO
Option C is correct because it used "of such infections as" But, of course, C would
still be appropriate if it had been

"what they had not previously considered possible -- better control, if not eradication, of such infections as..."
The use of "what" vs "something" does not distort the validity of option C.

To your questions.
In general, coordinating conjunctions are used to join 2 or more parallel items in a sentence.
They are FOR, AND, NOR, BUT, OR, YET, and SO. Acronym is: FANBOYS
Whereas, subordination conjunctions connect a subordinating clause to a main clause.
e.g. since, because, although, unless etc.

Let me know if you need further explanations (and experts please correct me where am wrong)

Option A: you can't use "the" with "other", "the other infections" is wrong.

"What" shows the specification and something is rather general.