The term which is considered as being undefined is referred to as a point and is therefore denoted as option A in this context.
This is defined as as small round mark written on a plane which signifies the position or location of a substance. This can also be seen as a dot and is also used to separate a group of numbers such as in the case of decimals etc.
It is referred to as being undefined alongside a plane, line etc as a result of it only being explained using specific examples and descriptions unlike a segment which can be viewed and understood easily when working on the parameter.
This is therefore the reason why a point is undefined and the most appropriate choice.
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