单选题. ① In 1755 British writer Samuel Johnson published an acerbic letter to Lord Chesterfield rebuking his patron for neglect and declining further support. ②Johnson's rejection of his patron's belated assistance has often been identified as a key moment in the history of publishing, marking the end of the culture of patronage. ③However, patronage had been in decline for 50 years, yet would survive, in attenuated form, for another 50. ④Indeed, Johnson was in 1762 awarded a pension by the Crown—a subtle form of sponsorship, tantamount to state patronage. ⑤The importance of Johnson's letter is not so much historical as emotional; it would become a touchstone for all who repudiated patrons and for all who embraced the laws of the marketplace.37. The author of the passage mentions Johnson's 1762 pension award in order to ______