I have a worksheet with many questions of them. I also have these two ones. Just can not clean them or write the whole worksheet again,but giving the questions whose answers I dont know to the students doesnt seem logical, too.I can see where you're going with this, but it's a bit of a tricky one. I don't think either "the mountain is grassy enough to climb" or "the soup is bland enough to eat" make much sense. Maybe you should pick adjectives that have clearer antonyms:
"He is too tall to fit in the tunnel, but she is small enough to climb through the hole", for example.