Which process is occurring at the center of all active stars? a) fusion b) fission c) flatulation d) hydrogen decay

The answer is A) fusion. Occurring at the center of all active stars including our sun, this nuclear reaction of combining two hydrogen atoms, and using an enormous amount of heat, forms a single more massive helium atom. This fusion of hydrogen atoms also produces the energy of the stars and creates the helium gases existing in the universe. 

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.