The correct answer is (a) May change.
An assessee’s residential status may change from year to year depending on a number of factors, such as the length of time they spend in India, their place of stay, and their intention to stay in India. If an assessee’s residential status changes, they may be liable to pay tax in India on their worldwide income, rather than just their income from Indian sources.
Option (b) is incorrect because it is not always certain that an assessee’s residential status will change from year to year. Option (c) is incorrect because it is possible for an assessee’s residential status to change from year to year. Option (d) is incorrect because it is not the only option that is correct.