Which two definitions of the word blessing does the pun in this excerpt rely on?
approval from someone in charge
a religious ceremony called a christening
encouragement from a friend
grace said at a meal
something that brings one happiness

B. A religious ceremony called a christening

E. Something that brings one happiness

 Oscar Wilde's comical play "The Importance of Being Ernest" revolves around the character of one gentleman John Worthing and his 'imaginary' alter-identity Ernest. John 'Jack' Worthing makes up the imaginary identity of Ernest whenever he wants to escape society and its responsibilities that he finds constricting and at times, absurd. And it was 'Ernest' that makes it possible for him to enjoy his life how he wants to.

 In the given excerpt from Act II, we see Jack asking the rector Chasuble to be rechristened. The use of the pun "blessing" in this excerpt is suggestive of the literal sense, the religious ceremony where babies are christened in front of God and the parents. It also means something that brings happiness and joy to a person.

the answer is irony!