Answer:
(b) 8 cm
Explanation:
You want to know the length of segment LN with midpoint M and the length of LM given as 4 cm.
Segment addition
The segment addition theorem tells you the length of a line segment is equal to the sum of the lengths of its parts.
LN = LM +MN
Markings
The hash marks on segments LM and MN mean those segments have the same length. Then the sum is ...
LN = (4 cm) +(4 cm) = 8 cm
The length of segment LN is 8 cm.