An electron is moving with an initial velocity $\overrightarrow{v} =v_0 \hat i$ and is in a magnetic field $\overrightarrow{B}= B_o \hat j$ Then its de -Broglie wave length

Question

$\begin{array}{1 1} \text{remains constant } \\ \text{increases with time} \\ \text{decreases with time} \\ \text{increases and decreases } \end{array}$