If they rub together it can make earthquakes and cause landslides or buildings to topple.
Answer:
I think it is the last one
Answer;
-Bone tissue becoming stronger.
The mechanical stress applied to bones during moderate physical exercise leads to bone tissue becoming stronger.
Explanation;
-Bones and muscles both become stronger when muscles push and tug against bones during physical activity.Swimming and bicycling are not weight-bearing activities, so they do not directly help build bones. But swimming and bicycling do help build strong muscles, and having strong muscles helps build strong bones.
-Weight-bearing physical activity causes new bone tissue to form, and this makes bones stronger. This kind of physical activity also makes muscles stronger. Bones and muscles both become stronger when muscles push and tug against bones during physical activity.
