select the undefined term that best defines the arrow pictured

Answer: A line is the undefined term which best defines the arrow pictured
Step-by-step explanation:
There are three undefined terms in geometry are as follows
1) point → has no dimensions
2) line → has one dimension
3) plane. → has two dimensions
In the given picture, a line is the only undefined term which best fits to define the arrow pictured since arrow has only length, thus it has one dimension as a line.