What major muscle is this man contracting to push himself up while doing a push-up?

How does natural selection change thephenotypes within a population over time?

Many organizations release indexes used to measure the development of the world's countries. as we learned in this lesson, these indexes measure many factors, from life expectancy to happiness. in your opinion, what are the three most important factors we can use to determine how developed a country might be? explain your answers in a few sentences.

What amount of heat is exchanged when 106.2 grams of substance y goes from a liquid at 35 degrees