According to the results the correct hypothesis was that seeds can germinate if we water them with plain water or with a small quantity of salt. So just 8% of the students proved right. 

If the medium is too salty cells dehydrate trying to reduce the concretation of salt and balance the pressure. In consequence they die. Salt is a big toxic for plants.

A very acid medium is not a good environment for seeds to grow. Acid damages the seeds. This is the effect of the acid rain on plants and seeds. Acid rain is due to the use of non-renewable sources of energy such as fossil fuels. This is another reason for substituing petrol by clean energy resources.