1)

The work done by an uniform magnetic field on a moving charge is

A) zero because $\overrightarrow{F}$ acts parallel to $\overrightarrow{v}$

B) positive because $\overrightarrow{F}$ acts perpendicular to $\overrightarrow{v}$

C) zero because $\overrightarrow{F}$ acts perpendicular to $\overrightarrow{v}$

D) negative because $\overrightarrow{F}$ acts parallel to $\overrightarrow{v}$

$\overrightarrow{F} = q (\overrightarrow{v} \times \overrightarrow{B})$ where $\overrightarrow{F}$ is perpendicular to $\overrightarrow{v}$ .
Work done/sec = $\overrightarrow{F}$.$\overrightarrow{v}$ = Fv cos90º= 0