Step 1: Structure of seed coat.
The seed coat consists of two layers: outer testa and inner tegmen.
Step 2: Protective role.
The testa is thick and tough, providing protection against mechanical injury, dehydration, and adverse environmental conditions.
Step 3: Analysis of options.
(A) Testa: Correct. It is the outer protective layer of seed.
(B) Tegmen: Incorrect. It is thin and lies beneath testa.
(C) Scutellum: Incorrect. It is a cotyledon in monocots.
(D) Endosperm: Incorrect. It provides nourishment, not protection.