The singular "Eggplant, onion, celery" should also be marked correct.
Celeries (the plural form of "celery") should also be acceptable.
I guess...though only if you are talking about various varieties of celery. If you have a few stalks of celery, you just have 'celery' not 'celeries'
We call eggplant "aubergine" in the UK but this was marked wrong - this should be fixed