The Rosenmund reaction is a hydrogenation process where molecular hydrogen reacts with the acyl chloride in the presence of a catalyst – palladium on barium sulphate. Barium sulphate reduces the activity of palladium due to its low surface area, thereby preventing over reduction.

It is known as rosenmund reduction, which is the partial reduction of acid chloride to aldehyde.
Hence, the answer is option A.
