Answer: A, C
Isopropylmagnesium bromide with CO2 gives 2-methylpropanoic acid (correct). With HCHO it gives 2-methylpropan-1-ol, but Structure B (3-methylbutan-2-ol) is the ethanal product, so B is wrong. With acetone it gives 2,3-dimethylbutan-2-ol (correct). With ethylene oxide it adds two carbons, giving 3-methylbutan-1-ol; Structure D has three carbons added, so D is wrong.