"hand-in"

A portrait type that appeared with relentless frequency in eighteenth-century England is the familiar image of a gentleman poised with one hand inside his partially unbuttoned waistcoat. Standard interpretations of this portrait posture offer observations of correspondence—demonstrating either that it mirrors actual social behavior or that it borrows from classical statuary. Such explanations, however, illuminate neither the source of this curious convention nor the reason for its popularity. It is true that in real life the "hand-in" was a common stance for elite men. Still, there were other ways of comporting the body that did not become winning portrait formulas. And even if the "hand-in' portrait does resemble certain classical statues, what accounts for the adoption of this particular pose?

Which of the following might provide an explanation for the popularity of hand-in portraits that would satisfy the author of the passage?

❑ An eighteenth-century English etiquette manual discussing the social implications of the "hand-in" stance
❑ A comprehensive catalogue of eighteenth-century English portraits that showed what proportion of portraits depicted gentlemen in the "hand-in" stance
❑ A passage from an eighteenth-century English novel in which a gentleman considers what stance to adopt when his portrait is painted

structure:

A common posture is the "hand in" portrait in 18th 

The interpretation of this phenomenon is that it demonstrate 1) mirror actual social behavior 2) borrows from classical statuary--TBD

For author, this explanation cannot resemble the fact 1) the source of this curious convention 2)  the reason for its popularity

to support author, the explanation should include the source of curious convention and the reason for its popularity

or other person also find the traditional explanation cannot be well explained to the source and the reason for this popularity.