YDS 2018-2 Soru=17

Sometimes when people assert that a language has no
grammar, what they really mean is that there is no
grammar book for that particular language. But the rules
of a language (17)---- in the heads of speakers of that
language. We know the rules are there (18)---- the way
the speakers behave. They use similar structures
(19)---- similar events. If you hear the sentence for
“Give me some water.” in a rarely spoken language
such as Spelitzian, you can be pretty sure you can use
the same pattern for “Give me some food.”, (20)---- there
are other possible patterns as well. If there were not any
patterns, people would not be able to communicate
because they would have no way of knowing what other
people meant (21)----.