Final answer:
The plate treated with gibberellin likely had the highest germination rate as gibberellins stimulate seed germination, unlike abscisic acid, cytokinin, or ethylene which play other roles in plant development.
Step-by-step explanation:
In an experiment designed to release seeds from dormancy using various hormones, the plate with the hormone gibberellin likely showed the highest rate of germination. Gibberellins (GAs) play a critical role in stimulating seed germination among other growth processes in plants. In contrast, abscisic acid generally works to maintain dormancy under unfavourable growth conditions and cytokinin along with ethylene have different roles in the plant's growth and development that are not directly related to breaking seed dormancy.