Which of the following can’t be observed in the same flower ?
A. Two types of placentation
B. Two types of aestivations
C. Stamens of two different heights
D. Two types of structural symmetry

Two types of placentation and two types of structural symmetry cannot be seen in the same flower. But the calyx and corolla can have two different types of aestivation. For example some members of fabaceae family can have valvate aestivation corolla of and vexillary aestivation of corolla. Stamens of two different heights are seen in members of Brassicaceae family.