I believe your answer would be the stem.
Mechanical waves cannot move without a medium
Answer:
1. A massive star depletes its nuclear fuel; gravity overpowers the star; supernova occurs; core of star collapses
2. black hole; gravitational pull
3. The center of the Milky Way
Explanation:
Answer:
The answer is animal actions
Explanation:
It said it in the guided notes associated with the lesson.