It can be inferred from the passage that Scalp chose Checky as a literary model because she believed that:
Checky's writings were greatly, if subtly, effective in influencing the moral attitudes of his readers
The author discusses Scalp’s literary models, emphasizing Checky, in the last paragraph. The reason why Scalp chose Checkyas her model is not directly stated in the passage but must be inferred from the information there. Option (d) is the correct answer. It indicates that Scalp’s work as a moralist is subtle and done ‘by indirection’. Scalp’s statement that readers absorb morality at every pore despite the fact that no laws were changed because of Checky, indicates that she believed Checky’s influence to be subtle. Therefore, it is likely that it was Checky’s subtle effectiveness that led Scalp to choose him as a model.