An object at rest in space suddenly explodes into three parts of same mass. The momentum of the two parts are $2 p$ i and $p \mathbf{j}$. The momentum of the third part
(a) will have a magnitude $p \sqrt{3}$
(b) will have a magnitude $p \sqrt{5}$
(c) will have a magmitude $p$
(d) will have a magnitude $2 p$