(2008? Xiao Li was very interested in the germination of seeds, so he did the following experiment according to the pictures: drying similar plants with the same vitality and exuberance.

Seeds A and 2 can contact air on the water surface, get proper moisture, sufficient air and appropriate temperature, and have external conditions for seed germination, so their germination ability is the strongest, which is in line with the meaning of the question.

The contrast condition of B, ① and ② seeds is water, not air.

C, because there are three seeds submerged in water, the seeds can't get enough air. The contrast condition between ② and ③ is that there is enough air instead of water, which doesn't meet the question.

Seed germination needs proper amount of water, sufficient air and suitable temperature. This experiment can only show that seeds need air and water for germination, but can't prove that they need temperature.

So choose: a