It is possible to give wedding presents, birthday and Christmas presents, without any thought of affection at all, they can be ordered by postcard, but the unbirthday present demans the nicest care. It is therefore the best of all, and it is the only kind to which the golden rule of present-giving imperatively applies - the golden rule which insists that you must never give to another person anything that you would not rather keep: nothing that does not cost you a pang to part from. It would be better if this rule governed the choice also of those other three varieties of gifts, but they can be less exacting.
The 'unbirthday' present is the best of all because

Options

A. it cannot be ordered by postcard
B. it means giving expensive presents
C. its choice needs the utmost care
D. other occasions are better than birthdays for giving presents