Select the correct answer for each question (only one answer per question). If you select an answer and then change your mind, make sure you uncheck your previous answer. 1. Find the most suitable form (with the minimum amount of terms) for a particular solution of y" + 4y - -4est + t sin(2t) if the method of undetermined coefficients is used. OA. Up = Aest + Btsin(2t) OB. Up = Aest + Bsin(2t) + C cos(2t) OC. Up = Aest + (Bt + C) sin(2t) + (Dt + E) cos(2t) OD. Up = Atest + Btsin(2t) + Ct cos(2t) DE. Up = Aest + t(Bt + C) sin(2t) + t(Dt + E) cos(2t) OF. none of the above 2. The phase portrait of the system = dz = -y, dt dy = ax consists of: OA. circles OB. parabolas Oc. ellipses OD. lines through the origin OE. hyperbolas OF. none of the above