Correct Option: B

We know that energy of a signal is given as
E = ∫^∞_–∞ |f(t)|²dt
Consider energy for signal f(2t) is E′
then E′ = ∫^∞_–∞ |f(p)|²dp
Let 2t = p

dt =	dp
	2

E′ = ∫^∞_–∞ |f(t)|² dt 2

E′ =	E
	2

(∵ by using change of variable property)
Hence, alternative (B) is the correct choice.