The original sentence is indeed inverted, with the main verb preceding the main subject.
A: From studies...come what scientists know.
Here, the subject of come (plural) is what scientists know (singular).
If we reorder the sentence, we get:
What scientists know come from studies.
Since the subject (what scientists know) is singular, while the verb (come) is plural, eliminate A.
Choice B – This choice has three errors as noted below.
Redundant – “knowledge that scientists know” is redundant expression
Punctuation error – “that is, the cranium” = The verb is unnecessarily separated from the object by comma
Modifier “that is, the cranium” distorts the intended meaning = Per the original sentence, cranium is the bony house of brain. However per this choice, cranium is the back of the skull. This is because “that” refers to ‘back of the skull’.
Choice C – This choice has SV number disagreement error. The SV pair – “knowledge-come” does not agree in number.
come (plural) does not agree with the knowledge that scientists have (singular).
Choice D – No Errors
Choice E – This choice has three errors as noted below.
Redundant – “know what they know” is redundant expression
Wordy & Awkward construction – “it is from studies of this that…”
Pronoun – This is used as a pronoun to refer to cranium. We cannot use “this” in this role without adding a noun after it for example, “this part” would have been correct in the context of this sentence.
Thus, choice D is the correct answer.