How many stereoisomeric d-aldopentoses are there?

There are eight stereoisomeric d-aldopentoses. Aldopentoses have five carbon atoms, with one carbonyl group (aldehyde) and four chiral centers, leading to (2^4 = 16) possible configurations. However, because of the presence of the aldehyde group, only half of these configurations correspond to d-aldopentoses, resulting in eight distinct stereoisomers.