What is the ratio of the total sales of branch B2 for both years to the total sales branch B4 for both years?

Answer: Option C

Required ratio
$$=\frac{\text{Total sales of branch B2 for both years}}{\text{Total sales of branch B4 for both years}}$$
$$\begin{array}{rl}& =\frac{75+65}{85+95}\\ & =\frac{140}{180}\\ & =\frac{7}{9}\\ & =7:9\end{array}$$