Final answer:
Option (d), The experiment with differing light schedules suggest that the blooming shrubs are short-day plants, needing prolonged darkness to initiate flowering.
Step-by-step explanation:
From the experiment with the shrubs of the same species of woody plant under two different light schedules, we can conclude that the shrubs are likely short-day plants. These types of plants require a longer period of uninterrupted darkness to initiate flowering.
The set of plants that received 9 hours of light and consequently 14 hours of dark did bloom, which fits the criteria for short-day plants. In contrast, the set of plants under 15 hours of light did not bloom because the longer light period likely interrupted the necessary dark period.