Viruses cannot reproduce by themselves, and viruses attach themselves to cells and reproduce. Given these facts, how can viruses make copies of themselves among the following options:
- A compound that donates proton
 - attach themselves to cells
 - have sex with another virus
 - distances themselves from cell
 - attach themselves to viruses
 - it needs them
 - rapid expansion
 - By wind and rain


 

  attach themselves to cells       