The observation, ‘becoming seriousness’ has which one of the following meanings?

Question

Read the passage and answer the question.

Passage 4
It is with much satisfaction that I hear this great city enquiring day by day after these my papers, and receiving my morning lectures with a becoming seriousness and attention. My publisher tells me, that there are already three thousand of them distributed every day : so that if I allow twenty readers to every paper, which I look upon as a modest computation, I may reckon about three score thousand disciples in London and Westminster, who I hope will take care to distinguish themselves from the thoughtless herd of their ignorant and inattentive brethren. Since I have raised to myself so great an audience, I shall spare no pains to make their instruction agreeable, and their diversion useful. For which reasons I shall endeavour to enliven morality with wit, and to temper wit with morality, that my readers may, if possible, both ways find their account in the speculation of the day. And to the end that their virtue and discretion may not be short, transient, intermitting starts of thought, I have resolved to refresh their memories from day to day, till I have recovered them out of that desperate state of vice and folly, into which the age is fallen. The mind that lies fallow for a single day, sprouts up in follies that are only to be killed by a constant and assiduous culture. It was said of Socrates that he brought Philosophy down from heaven, to inhabit among men; and I shall be ambitious to have it said of me, that I have brought Philosophy out of closets and libraries, schools and colleges, to dwell in clubs and assemblies, at tea-tables and in coffee-houses.