Right choice is (b) False
Easiest explanation: Here we can see,
|x(t)|≤Bx<∞, for all t.
Using the input output relation we have y(t)= tx(y). And so we may write, |Y(t)|=|tx(t)|=|t||x(t)|=|t|Bx.
As tends to infinity, the output also tends to infinity. That is it is unbounded. So it is unstable.