What is homolytic bond fission?

Carbocations are formed by the heterolytic cleavage of a covalent bond. a) What is heterolytic bond fission?

In which of the following, homolytic bond fission takes place :

In which of the following, homolytic bond fission takes place :

In which of the following homolytic bond fission takes place ?

In which of the following, homolytic bond fission takes place :