(b) That's wrong. In establishing whether a duty of care exists, it is not necessary to show that a person in the position of the defendant would have foreseen harm to a particular plaintiff. But it must be shown that it was foreseeable that harm might be caused to members of a class or category of persons, such as 'other road users', and that the plaintiff was a member of that class.
This is a question of fact. The courts assess whether a person in the position of the defendant ought to have foreseen that their negligence would create a risk of harm to those persons who are likely to be 'closely and directly' affected by their actions. If the person actually harmed is outside that category or class of persons, the plaintiff's harm will not be considered reasonably foreseeable.
In Palsgraf v Long Island Railroad Co, 248 NY 339 (1928), on which the example in the question is based, it was held that there was no duty of care owed to the injured passenger. The majority view was that, even though the conduct was careless, there was no liability to C, towards whom harm could not be anticipated.