Q$1)$ The lifetime of the pion is $2\mathrm{.}6{10}^{-8}s$ and its speed is $0\mathrm{.}998c$ then the distance it travels before it decays is

A$)10400m$

B$)1040m$

C$)123m$

D$)233\mathrm{.}5m$

Q$2)$ How many different meson combinations can you make with $2$ differe