Concept:"Scarcely" means "hardly" or "barely," and it shows that something is true only to a very small degree.
Explanation:The sentence shows that the speaker has very little acquaintance with the person concerned.
As a result, the speaker would not be willing to lend the books to that person.
"Often" means frequently, so it cannot express limited knowledge.
"Seldom" and "rarely" mean "not regularly," but they still describe repeated actions rather than a near-total lack of knowledge.
"Scarcely" carries the sense of "almost not at all," which best fits the idea that the speaker hardly knows the person.
Therefore, the word that correctly completes the sentence is "scarcely."
Answer:D. scarcely