Given that there is one zone where no company sold
Frisbees. Let Z4 be such a zone.
Assume that A sells Frisbees in zone Z1, so the other
company that sells Frisbees in Z1 has to be E.
Since G has three competitors, therefore the number of
companies selling Frisbees in the zone where G sells is 4.
Lets assume G sells in Z2, therefore the complete list of
companies selling Frisbees in Z2 is E, G, C and H.
The same holds true for B, which has three competitors.
Lets assume B sells in Z3, therefore the complete list of
companies selling Frisbees is E, B, C and H.
Now, since the number of competitors of D and F are 4
each the complete list of companies selling Frisbees in Z5 will
be E, D, F, C and H.
The following table can be made now.

$\begin{array}{cc}ZONE& COMPANIES\\ Z1& A,E\\ Z2& E,G,C,H\\ Z3& E,B,C,H\\ Z4& 0\\ Z5& E,D,F,C,H\end{array}$

A has exactly one competitor. If you look at the table , A can have 0 competitors by being present in Z4 and 1 competitor by being present in Z1. Thus, the answer is option option (c)