Astudent is testing water to know which is best for cleansing purposes with soaps. he would find that the cleansing action of soaps is best when he uses water obtained from
a. rain
b. tap
c. hand pump
d. pond

The excretory system,need answers for all: )

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

Element before carbon on the periodic table