2-Methyl propyl bromide reacts with `C_2H_5O^-` and gives 'A' whereas on reaction with `C_2H_5OH` it gives .The mechanism followed in these reactions and the products 'A' and 'B' respectively are :

Options

A. `S_n1`, A = tert -butyl ethyl ether, `S_n2`, B = iso-butyl ethyl ether
B. `S_n2`, A = 2-butyl ethyl ether, `S_n2`, B = iso-butyl ethyl ether
C. `S_n1`, A = tert -butyl ethyl ether, `S_n1`, B = 2-butyl ethyl ether
D. `S_n2`, A = iso-butyl ethyl ether, `S_n1`, B = tert-butyl ethyl ether