-In the Above Table,the Cross Price Elasticity of Demand for
\text

$$\begin{array} { l r r r r r r } \text { Month } & \mathbf { P X } _ { \mathbf { X } } & \mathbf { Q X } & \mathbf { P } _ { \mathbf { Y } } & \mathbf { Q } & \mathbf { P } _ { \mathbf { Z } } & \mathbf { \text { QZ } } \\\hline \text { Jan } & \$ 10 & 100 & \$ 20 & 50 & \$ 25 & 200 \\\text { Feb } & 10 & 90 & 18 & 60 & 25 & 225 \\\text { Mar } & 10 & 70 & 15 & 90 & 25 & 275 \\\text { Apr } & 12 & 50 & 15 & 100 & 25 & 290 \\\text { May } & 15 & 25 & 15 & 120 & 25 & 320\\\hline\end{array}$$
-In the above table,the cross price elasticity of demand for good X with good Y when PY falls from $20 to $18 is

A) -2.
B) 0.
C) +1.
D) -1.