The correct option is C ₹3000
She will earn ₹300 every 3rd day.
Thus, days on which she will earn the money will be multiples of 3, i.e. 3, 6, 9, 12, 15, 18, 21, 24, 27, 30
Thus, there will be 10 such days.
Total money she will earn = 10 x ₹300 = ₹3000