If instantaneous current is given by $\mathrm{i}=4\cos (\mathrm{\omega t}+\mathrm{\varphi })$ amperes, then the r.m.s. value of current is

• A

  4 amperes

• B

  $2\sqrt{2}\text{ amperes }$

• C

  $4\sqrt{2}\text{ amperes }$

• D

  Zero