若集合 $M=\{x \mid \sqrt{x} < 4\}, N=\{x \mid 3 x \geq 1\}$ ，则 $M \cap N=$
A
$\{x \mid 0 \leq x < 2\}$
B
$\left\{x \left\lvert\, \frac{1}{3} \leq x < 2\right.\right\}$
C
$\{x \mid 3 \leq x < 16\}$
D
$\left\{x \left\lvert\, \frac{1}{3} \leq x < 16\right.\right\}$
E
F