Here it is
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Glycerol and  pottasiumhydrogensulfate gives acroleine CH2=CH-CHO , reductionwith Alanate gives Propanale CH3CH2CHO

Sodium hydrogen sulphate (NaHSO₄)acts like a dehydrating agent which results in the dehydration of glycerol to acrolein. Then aldehyde group of acrolein can be reduced by lithium aluminum hydride to give alcohol.
Alkene pi bond can not be reduced by metal hydrides like sodium boron hydride NaBH₄ or lithium aluminum hydride (LiAlH₄).