which best describes era and periods? a) eras have a smaller time span than periods. b) eras and periods are independent of each other. c) eras and periods both appear at the start of the Cambrian period. d) Eras were more recently established on the time scale than periods ​PLZ HELP I DONT HAVE MUCH TIME

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.

How have high taxes on tobacco products impacted the number of people who use them? a. the number of tobacco users has increased. b. the number of tobacco users has decreased. c. the number of tobacco users has not changed. d. the number of adolescent tobacco users decreased, while the number of adult users increased

Why does the earth spin slowly, not faster? is it possible to prove it scientifically? can you prove it with math?