Explanation : The immediate inference for ‘No man is infallible’
is ‘No infallible (persons) are men’. So conclusion II is
right. In logical form, the opposite of infallible may not
be fallible. So inference may not apply. So, option (a) is
Explanation : Since the middle term ‘trains’ is not distributed
even once in the premises, no definite conclusion fol-
lows. However, III is the converse of the second premise, while IV is the converse of the first premise. So,
both of them hold.