Question

1. choose the best answer. what is a characteristic of bone - strengthening activities? vertical effort exercise over time impact against the ground resistance against work

Explanation:

Bone - strengthening activities typically involve impact against the ground. This impact creates mechanical stress on the bones, which stimulates bone remodeling and strengthening. Vertical effort is too vague. Exercise over time is a general concept for many types of exercises (not specific to bone - strengthening). Resistance against work is more related to muscle - strengthening (like weight - lifting which is a form of resistance training for muscles, but the key for bone - strengthening is the impact).

Answer:

impact against the ground