How is the mass number calculated for an element? a. the difference between the mass and the protons b. there is no calculation. c. the product of neutrons and protons d. the sum of protons and neutrons

The best answer is D.

The mass number of an element is the sum of the number of protons and the number of neutrons. Protons and neutrons both weigh about one atomic mass unit or amu.

The nucleus of an atom is made up of protons and neutrons. Both these two types of particles are almost the same size.  Almost all the mass of an atom (99%) is in the nucleus. Atomic mass therefore is really a measure of the size of the nucleus.

i believe you meant to say air rather than hair so the answer is below ")

the dead sea, the lowest place on earth at 430 metres (1,410 ft) below sea level, has a correspondingly high typical atmospheric pressure of 1065 hpa.

kelp are large brown algae that live in cool, relatively shallow waters close to the shore. they grow in dense groupings much like a forest on land. these underwater towers of kelp provide food and shelter for thousands of fish, invertebrates, and marine mammal species.

e) all of the above