observe the given reaction, $n-Bu\tan e\underset{h\upsilon }{\overset{C{l}_2}{\to }}$, the total number of mono-chloro products (Including stereo isomers) which are possible in this reaction.

1-Chloro butane and 2-chloro butane are the two structure isomers obtained.  But  2-chloro butane contains chiral carbon, hence it can give rise to two isomers. Totally 3 isomers.