An undefined term in geometry is a basic concept that does not have a formal definition but can be described and understood through examples and properties. Among the options provided, the statement that best fits this description is:
"A point looks like a period."
This suggests that a point is a basic concept (or undefined term) in geometry that does not have a specific definition but can be approximated visually. Points, lines, and planes are all considered undefined terms in geometry, whereas the other options contain inaccuracies (e.g., a plane does not have edges, and a line extends infinitely in both directions, not just one).
The best answer to identify an undefined term in this context is:
A point looks like a period.