Step 1: Understanding the context.
The sentence describes a person who is self-centred and has the qualities necessary to write essays. The words used must reflect the personality traits and the stamina required for writing.
Step 2: Analyzing the options.
(A) brutally, canter: "Brutally" implies harshness, which is not consistent with the concept of being self-centred in a positive sense. "Canter" refers to a moderate speed of horse riding, which doesn't fit with the context of writing essays. This option is incorrect.
(B) conscientiously, endurance: "Conscientiously" refers to working with care, which contradicts the idea of being self-centred. "Endurance" fits with stamina, but this pair doesn’t fit the overall tone.
(C) selfishly, diffidence: "Selfishly" fits the idea of being self-centred, but "diffidence" means shyness or lack of confidence, which is the opposite of stamina or assertiveness needed to write essays. This option is incorrect.
(D) congenially, effrontery: "Congenially" means being pleasant and friendly, which contradicts the self-centred nature described. "Effrontery" means shamelessness, but it doesn't fit with the context of stamina for writing. This option is incorrect.
(E) venally, inspiration: "Venally" refers to being motivated by self-interest or greed, which fits the description of a self-centred person. "Inspiration" fits well with the stamina and drive needed to write essays. This option fits best.
Step 3: Conclusion.
The correct pair of words is (5) venally, inspiration, as it logically fits the sentence context.