For life to begin, simple molecules had to be formed and then organized into complex molecules. fill in the blank

The breakdown of food is accomplished by enzymes. a. physical b. chemical c. mechanical d. none of the above

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 organs comprise the respiratory system of a bird