Mark each of the following true or false. 

___ a. Every proper subgroup of a free group is a free group. 

___ b. Every proper subgroup of every free abelian group is a free group. 

___ c. A homomorphic image of a free group is a free group. 

___ d. Every free abelian group has a basis. 

___ e. The free abelian groups of finite rank are precisely the finitely generated abelian groups. 

___ f. No free group is free. 

___ g. No free abelian group is free. 

___ h. No free abelian group of rank > 1 is free. 

___ i. Any two free groups are isomorphic. 

___ j. Any two free abelian groups of the same rank are isomorphic.