Correct Option is (C)

Acceleration of Car, a_C = 4 m/s²

Acceleration of bus, a_B = 2 m/s²

Initial distance between them, S = 200 m

Acceleration of Car with respect to bus,

a_CB = a_C $-$ a_B = 4 $-$ 2 = 2 m/s²

As initially both are at rest so, u_CB = 0

$\therefore$ S = U_CB $\times$ t + $\frac{1}{2}$ a_CB $\times$ t²

$\Rightarrow$$$ 200 = 0 + $\frac{1}{2}$ $\times$ 2 $\times$ t²

$\Rightarrow$$$ t² = 200

$\Rightarrow$$$ t = 10$\sqrt{2}$ sec.