Answer:
B. It decreased by 25% every year.
Explanation:
We have,
Number of subscribers 'y' after 't' years is given by,

i.e.

i.e.

We see that the rate of number of subscribers is -0.25 i.e. -25%.
Since, the rate is negative.
Hence, we get that the number of subscribers are decreasing 25% every year.