Final answer:
The expression that expresses the sentence "if a person is a hiker, then that person climbs mountains" is H(x) => M(x).
Step-by-step explanation:
The expression that expresses the sentence "if a person is a hiker, then that person climbs mountains" is:
H(x) → M(x)
This statement uses the arrow notation to represent the conditional relationship between being a hiker (H(x)) and climbing mountains (M(x)). It means that if a person is a hiker, then that person also climbs mountains.