\[\begin {array} {1 1} (a)\;\frac{-(1/3)^x}{\log 3}+\frac{(1/2)^x}{\log 2}+c \\ (b)\;\frac{(1/3)^x}{\log 3}+\frac{(1/2)^x}{\log 2}+c \\ (c)\;\frac{-(1/3)^x}{\log 3}-\frac{(1/2)^x}{\log 2}+c \\ (d)\;None \end {array}\]