In chlorophyII-b, the porphyrine ring is attached to the:

Explanation

The porphyrin ring in chlorophyll-b is specifically attached to an aldehyde group, which includes a carbonyl group (C=O) bonded to a hydrogen atom. This distinguishes it from chlorophyll-a, where the attachment is a methyl group. Methyl groups (CH3) are simple carbon groups not present in chlorophyll-b's structure. Carboxyl groups (COOH) and hydroxyl groups (OH) are not involved in the attachment of the porphyrin ring in chlorophyll-b.