D). To indicate that Twain needed money in order to eat
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Explanation:
Idioms are the most commonly employed figurative device to propose a sharp and rich language that conveys a meaning distinct from the literal meaning of the words presented. Such a device assists to present a more elaborate and spicier description offering an indirect meaning.
As per the question, the given idiom 'I..........book' functions to indicate that 'Twain required money to eat'. Twain was a realist who aimed to portray the real-life subjects with a touch of subtle elements. In this excerpt from his "I Sell a Dog", he intends to hint that he needed money for 'bread and butter'(eat). Thus, <u>option D</u> is the correct answer.
All the other ones would result in an incomplete understanding of the text. Slowing her pace at parts that she struggles with will help Sabrina understand the text more thoroughly.