N, N-dimethyl ethanamide on reduction with ${\mathrm{LiAlH}}_4$  gives;

 N, N-dimethyl ethanamide on reduction with ${\mathrm{LiAlH}}_4$ gives N, N-dimethylethanamine. Following is the reaction that takes place;

Hence, the correct answer is option B) N, N-dimethylethanamine.