(A) Tetragonal and Hexagonal unit cells have two edge lengths equal.
a=b≠c
(B) Cubic and Rhombohedral are two different crystal systems.
They ave equal edge lengths a=b=c
(C) Monoclinic and Triclinic are two different crystal systems and have all three edge lengths different.a≠b≠c
(D) Cubic and Hexagonal are two different crystal systems.