This answer is not correct. Lithium aluminum hydride will react with an alcohol in an acid-base reaction and form an hydrogen gas, which would bubble out of the solution. The problem with this answer is that the attack of the reagent is on the hydrogen atom attached to the oxygen atom and both alcohols will react. The isopropyl alcohol would react a bit faster due to steric inhibition of the reaction but not enough so that you could make a reasonable decision as to which was which.