Concept: This question tests your understanding of floral symmetry, specifically identifying plants with zygomorphic flowers.

Why (B) is correct:

Zygomorphic (bilateral symmetry) flowers can be divided into two similar halves only in one particular vertical plane. Among the given options:

• Gulmohar (Delonix regia) has zygomorphic flowers.
• Cassia (Cassia fistula) also exhibits zygomorphic flowers.

Why other options are wrong:

• Mustard (Brassica campestris) has actinomorphic (radial symmetry) flowers.
• Datura (Datura stramonium) has actinomorphic flowers.
• Chilli (Capsicum annuum) has actinomorphic flowers.

Therefore, only Gulmohar and Cassia have zygomorphic flowers.

Common Mistake: Students often confuse actinomorphic and zygomorphic symmetry, especially in common garden plants.

NEET Tip / Mnemonic: Remember that most members of the Fabaceae (legume family), like Gulmohar and Cassia, typically have zygomorphic flowers. Think of a pea flower – it's clearly bilaterally symmetrical.

Correct Answer: (B)