Select the single best answer. compound a (c7h15br) is not a primary alkyl halide. it yields a single alkene (compound b) on being being heated with sodium ethoxide in ethanol. hydrogenation of compound b yields 2,4−dimethylpentane. identify compounds a and b. a is 3−bromo−2,4−dimethylpentane; b is 2,4−dimethyl−1−pentenea is 1−bromo−2,4−dimethylpentane; b is 2,4−dimethyl−2−pentenea is 1−bromo−2,4−dimethylpentane; b is 2,4−dimethyl−1−pentenea is 3−bromo−2,4−dimethylpentane; b is 2,4−dimethyl−2−pentene