The correct answer is Option D.
WOULD expresses the desire or wish to do something.
WOULDN'T is the negation of WOULD.
In the given sentence, the speaker is expressing his desire to become a tourist guide. He WOULDN'T mind becoming a tourist guide.
Thus Option D is the correct answer.
The remaining options are incorrect because:
WON'T is the contraction of WILL NOT.
CAN'T expresses inability.
MUSTN'T means voluntary and not compulsory.