Concept: This question tests your knowledge of different types of placentation in flowering plants, which refers to the arrangement of ovules within the ovary.

Why (A) is incorrect: In Pea (Pisum sativum), the ovules are arranged along the ridge on the ventral suture of the ovary, forming a single row. This type of placentation is characteristic of the family Fabaceae (Leguminosae) and is known as marginal placentation, not axile placentation.

Why other options are correct:

• (B) Dianthus - Free central: In Dianthus (and Primrose), the ovules develop on a central axis, and the septa are absent, making it free central placentation.
• (C) Papaver - Parietal: In Papaver (poppy), the ovules develop on the inner wall of the ovary or on peripheral part. The ovary is one-chambered but becomes two-chambered due to the formation of a false septum. This is parietal placentation.
• (D) Arhar - Marginal: Arhar (Pigeon pea, Cajanus cajan) belongs to the family Fabaceae, just like Pea. Therefore, it also exhibits marginal placentation.

Common Mistake: Students often confuse marginal and axile placentation, especially in legumes, as both involve ovules attached to a central or ridge-like structure.

NEET Tip / Mnemonic: Remember 'Marginal for Monocots (often) and Legumes' (though Pea is dicot, it's a classic example of marginal). For axile, think 'Axile in All Citrus and Tomato'.

Correct Answer: (A)