(b) That's wrong. Even when harm is foreseeable, a duty of care to prevent that harm usually only arises in recognised situations or circumstances. Specific situations that give rise to a duty of care to prevent foreseeable harm include the following:
when an occupier of property causes harm to persons entering the property, because of the state of the premises
when a road user causes harm to other road users
when harm is caused by one person to another with whom they have a contractual relationship
when a manufacturer causes harm to a consumer of that manufacturer's product
when harm is caused by one person to another with whom they have a fiduciary relationship
In the present case, the relationship between A and B (manufacturer and consumer) is one of those that has long been recognised as potentially giving rise to a duty of care. The list of established relationships that create a duty of care is not a closed list. In more unusual cases, the courts weigh up various factors which may point to a relationship sufficient to give rise to a duty of care.