Answer:
41 meters
Explanation:
To determine the change in the dolphin's depth, subtract the initial depth from the final depth. The initial depth was 20 meters below the surface, and the final depth was 21 meters below the surface. The change in depth is calculated as:
Change in depth = Final depth - Initial depth
Change in depth = 21 m - (-20 m)
Change in depth = 21 m + 20 m
Change in depth = 41 m
Therefore, the change in the dolphin's depth was 41 meters.