The given data shows the number of mobiles (in thousands) manufactured by companies C-1, C-2, C-3 and C-4 in 2017, 2018 and 2019.

Which company witnessed the highest increase in manufacturing from 2017 to 2018?

From the graph,

Increase in manufacturing from 2017 to 2018 for company C-1 (in thousands) = 65-59 = 6

Increase in manufacturing from 2017 to 2018 for company C-2 (in thousands) = 67-62 = 5

Increase in manufacturing from 2017 to 2018 for company C-3 (in thousands) = 71-68 = 3

Increase in manufacturing from 2017 to 2018 for company C-4 (in thousands) = 62-59 = 3

$$\therefore\ $$Company C-1 witnessed the highest increase in manufacturing from 2017 to 2018

Hence, the correct answer is Option B