Answer :
[tex]A.\ \frac{3}{3}\times\frac{5}{5}=1\times1=1\neq\frac{3}{5}\\\\B.\ 3\times\frac{1}{5}=\frac{3}{1}\times\frac{1}{5}=\boxed{\frac{3}{5}}\\\\C.\ 5\times\frac{1}{3}=\frac{5}{1}\times\frac{1}{3}=\frac{5}{3}\neq\frac{3}{5}\\\\D.\ \frac{1}{5}\times\frac{3}{5}=\frac{3}{25}\neq\frac{3}{5}\\\\\Rightarrow Answer:\boxed{B}[/tex]
