Which contrasting trait was not considered by Mendel in pea plant?

The correct answer is Option (4) → Leaf shape

Mendel studied seven pairs of contrasting traits: stem height, flower colour, flower position, pod shape, pod colour, seed shape and seed colour.

Option (1) Flower position — Studied.

Option (2) Pod colour — Studied.

Option (3) Seed shape — Studied.

Option (4) Leaf shape — Not studied. Mendel’s seven pairs were stem height, flower colour, flower position, pod shape, pod colour, seed shape and seed colour. Leaf shape is not among them.

NCERT Extract:
Mendel’s Laws of Inheritance – “… Mendel selected 14 true-breeding pea plant varieties, as pairs which were similar except for one character with contrasting traits. Some of the contrasting traits selected were smooth or wrinkled seeds, yellow or green seeds, inflated (full) or constricted green or yellow pods and tall or dwarf plants (Figure 4.1, Table 4.1).”