Jack has been to a lot of parties this month. He enjoyed (every - each) one of them.
There are 3 glasses, but (each-every) one has a different shape.
In the answer guide, the two questions are answered as 'every' but why?
If the sentence focuses on the group as a whole, the answer will be every while if the sentence focuses on the individuals, the answer will be each
But how can I know whether the sentence focuses on the group or the individuals?