$C{H}_{3}C{H}_{2}Br+Mg\stackrel{X}{\to }Y$. Correct statements are 

A) X is dry ether B) Y is Grignard's reagent C) the preparation must be kept away from moisture

D) In presence of moisture alkane is formed E) RMgX is a source of carbanion

$C{H}_{3}C{H}_{2}Br+Mg\stackrel{\text{dryether}}{\to }C{H}_{3}C{H}_{2}MgBr$

$C{H}_{3}C{H}_{2}MgBr$ is RMgX. It is an organometallic compound (Grignard's reagent) 

Bond between Mg & X is ionic, R & Mg is polar covalent

$\stackrel{\delta }{R}\stackrel{\delta +}{Mg}X$ is a source of carbanion

R-MgX + HOH (moisture) $\to$ R-H+ HO-Mg-X