The element calcium has the atomic number of 20 and the mass number of 40, how many neutrons dose it have

The mass number is the sum of the number of protons and number of neutrons the atom has.

So, we can write the equation as:

x + 20 = 40

x = 20 neutrons.

the right answer is a. skin cells forming from sunlight.

the liver is an organ endowed with a fantastic ability to regenerate

. thus, if a hepatectomy (ablation) of 70% of the hepatic mass is performed in the rat, there is complete recovery in 7 to 10 days.

prokaryotes are beings that have existed since the existence of life on earth, and do not come from another realm.

ribosomes are organelles that exist naturally in eukaryotes, either in free form or attached to the endoplasmic reticulum.

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