Read each sentence to find out whether there is any grammatical mistake/error in it. The error if any will be in one part of the sentence. Mark the number of the part with error as your answer. If there is 'No error' mark(d).
`("Though, she has aptitude in Mathematics")/a` `("I won't allow her to take it up as a subject of study for the Master's Degree")/b` `("because I know the labour involved will tell upon her health.")/c` `("No error")/d`.

Explanation

(a) Use .for. in place of .in.