Ovule integuments develop into the seed coat post-fertilization

Steps:

• Pollen tube grows through style into ovule via micropyle.
• Double fertilization: one sperm forms zygote (embryo), other forms endosperm.
• Ovule transforms into seed; surrounding layers differentiate.
• Integuments of ovule harden and dry to form protective testa.

Why C is correct:

• Testa is the seed coat derived from ovule integuments, per angiosperm reproduction anatomy.

Why the others are wrong:

• A (nucellus): Forms perisperm in some seeds, not testa.
• B (embryo sac): Develops into embryo and endosperm, not outer coat.
• D (micropyle): Entry pore that becomes seed scar, not protective layer.

Final answer: C