Yes we never know what could happen in an eco system
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 tissue that forms the outer surface of the body is a stratified squamous keratinized epithelium. The surface layer of dead cells(stratum corneum) is made to keep things out of the body, protecting it. The tissue that lines the digestive tract(e.g. intestine). Is made from 1 layer of columnar cells that facilitate the absorption of nutrients. Both tissues are epithelia.
The correct option is D. all of the above
