Which one of the following features of pea plant is not suitable for…

The correct answer is Option (4) → Stem tendril

Mendel chose seven pairs of contrasting traits in the garden pea: stem height, flower colour, flower position, pod shape, pod colour, seed shape and seed colour.

Option (1) Stem height — One of Mendel’s traits. Tall and dwarf were his best-known pair.

Option (2) Flower position — One of Mendel’s traits. Axial and terminal flowers.

Option (3) Pod colour — One of Mendel’s traits. Green and yellow pods.

Option (4) Stem tendril — Not one of Mendel’s traits. It is not among the seven pairs he studied.

Figure 4.1 Seven pairs of contrasting traits in pea plant studied by Mendel

NCERT Extract:
Mendel’s Laws of Inheritance – “… Mendel investigated characters in the garden pea plant that were manifested as two opposing traits, e.g., tall or dwarf plants, yellow or green seeds. This allowed him to set up a basic framework of rules governing inheritance, which was expanded on by later scientists to account for all the diverse natural observations and the complexity inherent in them.”