Temporal separation ensures cross-pollination in spikes

Steps:

• Flowers at base have mature carpels (female parts ready for pollen) but immature anthers (male parts not shedding pollen).
• Flowers at top have mature anthers (shedding pollen) but immature carpels (not ready to receive pollen).
• Bees first visit top flowers, picking up pollen on bodies without depositing any (no mature carpels there).
• Bees then visit base flowers, depositing pollen from top onto mature carpels, enabling pollination; second visit to new spikes repeats for ongoing success.

Why B is correct:

• Statement 2 aligns with dichogamy, where anther-carpel maturity differences prevent self-pollination and promote cross-pollination by forcing pollen transfer between flowers.

Why the others are wrong:

• A includes 3, which is false as seeds develop first at base (mature carpels receive pollen first).
• C includes 3, which misstates seed development sequence.
• D excludes 1, but bees must visit twice (top then base) for pollen pickup and delivery.

Final answer: B