Answer:
B). It is a noun clause indicating what Gregor was doing.
Step-by-step explanation:
A noun clause is demonstrated as the dependent or subordinate clauses which function as a noun in the sentence. These nouns can be employed as direct or indirect objects, subject, an object of the preposition, appositive, etc.
In the given sentence, the underlined clause is the noun clause as it functions as a noun in the sentence. It is used as the direct object in the sentence for signaling 'what Gregor was doing.' Thus, it answers this question that 'he was assessing how Sasha reacts to the news.' Therefore, option B is the correct answer.