Answer:

Explanation:
Beta emission involves the conversion of a neutron to a proton, an electron and a neutrino. This leads to a reduction in the neutron-proton ratio.
During a beta emission, the mass number of the parent and daughter nuclei remain the same. The atomic number of the daughter nucleus increases by one unit above that of the parent nucleus as we can see from the equation.
Hence, the daughter nucleus is found one place after its parent in the periodic table.
The boiling points need to differ by 50 degrees to enable their complete separation ie of two different liquids. The separation occurs by first evaporation of one of the liquids and then its condensation and collection. It is a physical process not a chemical one.
I would say C is the most correct.
In D it depends on what water source you're using. Let's say it is a waterfall, then the source of the water (melting ice or a lake) may disappear in the future.
If you're using underwater "windmills" placed in the ocean, then you would expect it to last a while as the ocean will not disappear in the near future.