The average distances of the planets from the Sun are given. Students are making a scale model of the Solar System. The school building represents the Sun and students are representing planets. The student representing Jupiter stands about 10 meters from the school. The student standing about 20 meters from the school is the student representing which planet? Mercury
Venus
Saturn
Uranus

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.