Mendeleev organized the elements
a. alphabetically by name.
b. by the number of electrons.
c. by increasing the atomic number and similar properties.
d. by increasing atomic weight and similar properties.

D

Explanation:

Mendeleev was a Russian scientist. His works provided the framework for the present day periodic table. What Mendeleev did was to arrange the elements in order of their atomic weights.

He however had some gaps in his periodic table. He impressively predicted the elements that would fill in these blank spaces even though they were yet to be discovered as at then.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.