The only statement that must be true based on the given information is KN = NM.
In triangle KNM, we have two sides that are given as equal: KN = NM. This means that the two sides opposite to vertices K and N have the same length.
Based on this information, we can deduce that the only option that must be true is:
1) KN = NM
This is because the other options imply different relationships between the sides of the triangle, which are not supported by the given information. For instance, option 2 (KN = NM = KM) suggests that all three sides of the triangle have the same length, which is not necessarily the case. Option 3 (KM = 2(NM)) implies that KM is twice the length of NM, which is not necessarily true either. Option 4 (KN = 1/2KM) suggests that KN is half the length of KM, which is again not necessarily true.
Therefore, the only statement that must be true based on the given information is KN = NM.