Correct Answer: 9175

Solution : As per the given graph:
In 2017, the sales of each brand increased by the same percentage as it did in the year 2016.
The increase in sales of Brand 1 in 2016 = $\frac{7.5-5.5}{5.5}×100=36.36\%$
The sales of Brand 1 in 2017 = $7.5+(7.5×\frac{36.36}{100})=10.2$ units
The increase in sales of Brand 2 in 2016 = $\frac{6-5}{5}×100=20\%$
The sales of Brand 2 in 2017 = $6+(6×\frac{20}{100})=7.2$ units
The increase in sales of Brand 3 in 2016 = $\frac{7.5-6.5}{6.5}×100=15.38\%$
The sales of Brand 3 in 2017 = $7.5+(7.5×\frac{15.38}{100})=8.6$ units
The increase in sales of Brand 4 in 2016 = $\frac{9.5-8.5}{8.5}×100=11.76\%$
The sales of Brand 4 in 2017 = $9.5+(9.5×\frac{11.76}{100})=10.6$ units
The approximate average sales (in 000 units) of mobiles per brand in the year 2017
= $\frac{10.2+7.2+8.6+10.6}{4}×1000$
= $\frac{36.6}{4}×1000=9150\approx9175$
Hence, the correct answer is 9175.