Answer: C
The primary NHX2 becomes NHCOCHX3 and the secondary NHCHX3 becomes N(CHX3)COCHX3, giving a diamide. LiAlHX4 reduces each amide carbonyl to CHX2, so each COCHX3 becomes an ethyl group on the same nitrogen. The product is CHX3CHX2NHCHX2CHX2N(CHX3)CHX2CHX3; no extra methyl group is added.