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

Ifound this on google “here are some features of the alveoli that allow this: they give the lungs a really big surface area. they have moist, thin walls (just one cell thick) they have a lot of tiny blood vessels called capillaries.for more information go to the website below › bitesize › guidesi hope this you for what your looking for. can you plz mark me brainliest?