【单选题】

Which of the following is NOT mentioned as one reason why energy problems cannot be easily solved
A．(A) There's a deep-rooted suspicion towards alternative energy among the public.

B．(B) Huge investments of various resources are required to achieve energy independence.
C．(C) Some oil producing countries are not politically stable.
D．(D) A large number of oil producing countries do not regard US as their friend.