Correct option (d) both (a) and (b)
Explanation:
Magnalium : 95% AI, 5% Mg. It is used in the construction of airships, weighing balance and pistons of motor engine.
Duralumin : 95% Al, 4% Cu,0.5 %Mg, 0.5'% Mn. it is used in aeroplanes and automobile parts.