100 kmph

110 kmph

120 kmph

130 kmph

C. 120 kmph

Let speed of the car be x kmph.

Then, speed of the train $=\frac{150}{100}x=\frac{3}{2}xkmph.$

$\therefore \frac{75}{x}-\frac{75}{(3/2)x}=\frac{125}{10x60}$

$\Rightarrow \frac{75}{x}-\frac{50}{x}=\frac{5}{24}$

$\Rightarrow x=\frac{25x24}{5}=120kmph.$