What is the role of electron transfer in chemical reactions

Atoms gain or lose electrons to increase their stability. The answer is letter C. Remember noble gases? They follow the octet rule in which their shells are electrons are filled with eight electrons. So the atoms that do not belong to the noble gas tend to be restless. They want their electrons to be filled to follow the octet rule. That is why they tend to share or gain electrons. Suppose you have a compound of CCl4. You know that chlorine can only share 1 electron because 7 of its electrons are filled. Also, in carbon, it can only share 4 electrons because 4 of it are already filled. That is why carbon needs four chlorine to form CCl4.

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.

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.