The overall argument can be broken down into 4 parts:
1. The perceptions of the scholars - that Wittgenstein (W) and Russel (R) developed their concepts on metaphysics of the language independently.
2. Many now argue - that since R's note were based on W's given R refers to W's note in his notes and that W's notes precede R's own conception, the traditional view held by scholars is wrong
3. Professor's (Author) take - This discovery based on which many have made their argument in pt 2 requires a more circumspect conclusion.
To support his point, the professor points out that - R's note refer to only some early part of W's note and that the early parts come before the main investigation into metaphysics of the language by W.
The two boldface:
i. "the notes...language" - This acts like an evidence or a support to the conclusion made by many in pt 2 above.
ii. the last sentence "Russel's notes... metaphysics of the language" - This is the premise that support's professor's conclusion that we fleshed out in pt 3 above.
Evaluation of the options:
A - The first is an evidence that supports the conclusion supported by the professor - incorrect. It is supporting the conclusion which the professor opposes.
B - Incorrect because of the same reason in A
C - Clearly fits into the analysis - The first boldface supports a conclusion which has been criticized by the professor, the second boldface acts as an evidence/support for the Professor's own conclusion. CorrectD - The first statement is used as a supporting for a conclusion but it is not a conclusion which acts an intermediate conclusion that support's professor's conclusion. Incorrect.
E - The first part is correct. However, the second boldface is not "Additional information" that supports the evidence presented in the first boldface. Incorrect.