B] \[{{(C{{H}_{3}})}_{3}}CBr+NaO{{C}_{2}}{{H}_{5}}\] can't be APPLIED for synthesising the ether because sod. ethoxide, being a STRONG base, will preferentially cause elimination reaction. \[{{\left( C{{H}_{3}} \right)}_{3}}CBr\xrightarrow{-O{{C}_{2}}{{H}_{5}}}{{\left( C{{H}_{3}} \right)}_{2}}C=C{{H}_{2}}+HBr\] In isobutene + ethanol, isobutene will form tert-butyl cation which reacts with ethanol, a nucleophile to form ether. \[{{(C{{H}_{3}})}_{2}}C=C{{H}_{2}}\xrightarrow{{{H}^{+}}}{{(C{{H}_{3}})}_{2}}\overset{+}{\mathop{C}}\,C{{H}_{3}}\] \[\xrightarrow[(ii)\,-{{H}^{+}}]{(i)\,C{{H}_{3}}C{{H}_{2}}OH}{{(C{{H}_{3}})}_{3}}COC{{H}_{2}}C{{H}_{3}}\]