The Price of X Falls by Ten Percent, and the Quantity

The price of X falls by ten percent, and the quantity demanded of X increases by ten percent. Meanwhile, the quantity demanded of Y increases by ten percent too. We would conclude that

A) demand for X is elastic, and X and Y are substitutes.
B) demand for X is elastic, and X and Y are complements.
C) demand for X is unit-elastic, and X and Y are complements.
D) demand for X is inelastic, and X and Y are unrelated.