Select the noun clause in each sentence Whatever you do make sure you're home on time.
Janice couldn't decide what she should major in at college

Noun clauses are dependent clauses acting as nouns. They begin with words such as how, that, what, who, whoever, whom, where, when, whether, which, whichever and why.  What is more, they can act as subjects, direct objects, indirect objects, predicative nominatives or as objects of prepositions.

Taking all this into account, the noun clauses found in the sentences presented are the following ones: "whatever you do" and "what she should major in at college".  In both cases, the noun clauses in question are actings as the subjects of the sentences.

whatever you do

what she should major in college

Explanation:

the answer is definitely d. sorry for a late response.