Why do children tend to have high-pitched voices, and why do males typically have lower voices than females do?

Children tend to have high pitched voice because the larynx is small and thin.

Males have lower voices because they have larger and thicker larynx.

Explanation:

Its the larynx that makes noise, so known as voice box. Changes in the length and thickness of larynx cause voice modulation. This modulation helps male getting a deeper voice.

The larynx of children are small and thin which helps to a high pitched voice and during the time of puberty, larynx starts growing and thickening.This makes the voice low pitched and deep.

Thus, its the thickening and thinning of larynx that helps in voice modulation.

b. read the phase at the intersection of any given temperature and pressure.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!