The correct option is (b) No hydrogenation
Easy explanation: If high-molecular-weight petroleum fractions are simply pryolyzed, i.e., if no hydrogenation occurs, then progressive cracking and polymerization generally lead to the final products: (1) gaseous and low-boiling liquid compounds of high hydrogen content, (2) liquid material of intermediate molecular weight and a hydrogen: carbon ratio differing more or less from that of the original feedstock, depending on the method of operation, and (3) liquid material of high molecular weight, such as tar and petroleum coke, possessing a lower ratio of hydrogen: carbon than the starting material.
