William Makepeace Thackeray wrote the novel Vanity Fair in 1846 and it was published as a 19-volume monthly serial from 1847 to 1848,
The novel takes place in the early 1800s, in the first years of the Victorian era, when the country was submerging into a strong and oppressive conservative way of life.
The plot tells the saga of two families during the Napoleonic wars.
From the definition of absolute phrases we know that it is a modifier that attaches to a sentence without a conjunctution. So, we can say "his chubby legs, pumping" is the correct answer.
