Ahmed is making a model of a vertebrate digestive system. Which of the following should NOT be included in his model? A. a single opening
B. mechanical digestion
C. chemical digestion
D. symbiotic microorganisms

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.