What is an example of a choice which is not necessitated by scarcity?
The basic idea behind scarcity and opportunity cost is fundamental to economics. Basically, if resources are infinite, you have everything.

In my opinion, there are no infinite resources because a lifetime is finite. In one way or another, it can be argued all choices are necessitated by scarcity.

Eating chips means at that time, you cant be eating a burger. That is your opportunity cost.

This may be the point of your homework question, to make you realise that scarcity is a key driving force behind decision making.