The correct option is C Cassia
Flowers in which the perianth segments within each whorl are bilaterally symmetrical about one vertical plane only is called as zygomorphic flowers. In imbricate aestivation, margins of petals overlap each other in such a way that one petal is completely external and one petal is completely internal, e.g., Cassia and Bauhinia.
Thus, the correct answer is option D.