Answer:
Region B in the Venn diagram shows that it mass 1 amu.
Explanation:
Protons are positively charged and they are present inside the nucleus.
Neutrons are neutral and they are present inside the nucleus.
In the Venn diagram the region B is the intersection of protons and neutrons that shows the property of protons and neutrons which is same for both.
Neutrons and protons have only one common property:
" Mass of protons and neutrons are 1 amu."
Thus, region B in the Venn diagram shows that it mass 1 amu.