Aerobic activities a. enable muscles to use less oxygen than normal b. do not require voluntary muscle c. force muscle cells to use more vitamins and minerals for energy d. involve sustained, rhythmic contractions of certain large skeletal muscles

A. Enable muscles to use less oxygen than normal

Explanation:

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I’m going to guess these are the choices: a) recreational skiing developed in the mid-19th century b) it was originally invented as a way of getting from place to place in snowy regions c) downhill skiing is currently the only common form of the sport d) it mostly evolved from snowshoeing- if that’s the cases then the answer would be c) downhill skiing is currently the only common form of the sport