A. Small molecules easily pass between the phospholipids in the cell membrane. B. Substances move from an area of low concentration to an area of high concentration.
C. Transport proteins use energy to push large molecules across the cell membrane.
D. A vacuole opens to release substances into the area outside the cell.

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.