Define Aldehydes

Question

$\begin{array}{1 1} \text{(a) An organic substance formed when a hydroxyl group is substituted for a hydrogen atom in a hydrocarbon.} \\ \text{(b)An organic compound containing the group - CHO} \\ \text{(c) An organic compound containing the group C=O} \\ \text{(d) An organic compound containing the group COOH}\end{array}$