An alkyl halide (A) on reaction with magnesium in dry ether followed by treatment with ethanol gave 2-methylbutane. Write all the structures of (A)

Please help.

The reaction involves formation of Grignard reagent which on reaction with alcohol gives back the alkane.

The carbon skeleton structure will be alkyl halide and final alkane will be the same. It is an isobuthyl structure as given in the figure.
There are 4 possible structures for A as given in the figure.

(Halide is denoted by X)