A workplace supervisor argues: 'Every worker who handed in a medical certificate was put on the light-duty list. Bhaskar is on the light-duty list. So Bhaskar handed in a medical certificate.' Which of the following sets out the form of this reasoning, the letters standing for the terms used in it?

The rule carries certificate-holders onto the list, and the supervisor travels back along it from the list to a certificate. That is the form 'all A are B, this is B, so this is A', which fails because the list may also hold workers put there for reasons of their own. The second and third options set out forms that are valid, and the fourth begins from a premise the supervisor never states.