All but one of the following are assumed to remain the same while drawing an individual's demand curve for a commodity. Which one is it?

Question statement is wrong , all but not one ....should be the statement
Only then option c will be the right ans

The law of demand assumes the prices of other commodities to remain constant (substitutes, complementary). If it considers the price of the commodity under consideration to be constant then while drawing the demand curve, it will parallel to the X-axis. (And that can have different interpretations). The answer given (Option C) is incorrect. Please look into this as this is one of the very basic theories of microeconomics.

As we know that price of the concerned commodity is the major determinant of the demand for the same commodity, then how come it remains same?

Why is it so?

how?

question should be "all but not one of the .................. " and then the given answer can be accepted as a correct answer.
isn't it ?