This excerpt is ironic chiefly because the writer

"i confess i have often my doubts whether it is to any purpose. i know how unwelcome advice generally is; i know that those who want it most like it and follow it least; and i know, too, that the advice of parents, more particularly, is ascribed to the moroseness, the imperiousness, or the garrulity of old age."

a. reveals skepticism about advice and those who accept it - my answer
b. questions the qualifications of the elderly to dispense advice
c. admits that those most in need of advice often ignore it
d. compares the reluctance of youth to the enthusiasm of the elderly