複選題6. (5%) Which boundary value problems have nontrivial solutions? (Trivial solution is defined as y(x) = 0.)(A) y" + 2y' - 3y = 0； y(0) = 0, y'(1) = 0(B) y" = 0； y(-1) = 0, y(1) – 2y'(1) = 0(C) y" + y = 0； y(0) = 0, y(π) = 0(D) y" + y = 0； y(0) = 0, y(π) = 1(E) All of above