A proton of mass $1.67 \times 10^{-27} \mathrm{~kg}$ and charge $1.6 \times$ $10^{-19} \mathrm{C}$ is projected with a speed of $2 \times 10^{6} \mathrm{~m} / \mathrm{s}$ at an angle of $60^{\circ}$ to the $x$-axis. If a uniform magnetic field of $0.104 \mathrm{~T}$ is applied along $y$-axis, the path of proton is
(A) a circle of radius $=0.2 \mathrm{~m}$ and time period $\pi \times 10^{-7} \mathrm{~s}$.
(B) a circle of radius $=0.1 \mathrm{~m}$ and time period $2 \pi \times 10^{-7} \mathrm{~s}$.
(C) a helix of radius $=0.1 \mathrm{~m}$ and time period $2 \pi \times 10^{-7} \mathrm{~s}$.
(D) a helix of radius $=0.2 \mathrm{~m}$ and time period $4 \pi \times 10^{-7} \mathrm{~s}$.