Step 1: Define apomixis.
Apomixis is asexual reproduction where seeds form without fertilization. The embryo develops from somatic or gametophytic cells.
Step 2: Analyze the choices.
- Apomixis: Correct. This is seed/embryo development without fertilization. - Anthesis: Refers to the flowering period, not seed formation. - Self-incompatibility: Prevents self-fertilization in flowers. - Male sterility: Inability to produce viable pollen; unrelated to apomixis.
Step 3: Conclude.
Apomixis is the correct answer.
Final Answer: \[\boxed{\text{Apomixis is the development of seed without fertilization.}}\]