Answer:
3. Mowing the lawn
Explanation:
Aerobic exercise is any type of cardiovascular conditioning.
Mowing the lawn is the only thing that is actively moving.
Answer:

Explanation:
For sound waves we have v=d/t where v is the speed of sound and d the distance between the astronauts, while for electromagnetic waves we have c=D/t where c is the speed of light and D the distance between the spaceship and Earth. <em>We have written both times as the same</em> because is what is imposed by the problem, so we have t=d/v=D/c, which means:

And for our values:

Answer: The person sitting in the middle of the train sees the back of the train enter ing the tunnel before the front end comes out.
Explanation:
Answer: All of our energy comes from the sun, which is our nearest star. The sun sends out huge amounts of energy through its rays every day. We call this energy solar energy or radiant energy. Without the sun, life on earth would not exist, since our planet would be totally frozen.