The answers are B and D.

The sentence argues that composition instructors must demonstrate strong writing skills to be credible evaluators of academic writing. The first blank focuses on their role as judges or evaluators, while the second blank highlights the contradiction and damage caused when they fail to meet the standards they enforce.

Blank (i):
A. custodians: Custodians are caretakers or guardians. While instructors may “look after” standards, the sentence specifically emphasizes evaluating and judging writing, not merely maintaining it. Hence, this is not precise enough.
B. arbiters: Arbiters are judges or authorities who make decisions or evaluations. This fits perfectly because instructors assess, judge, and determine the quality of students’ writing.
C. proponents: Proponents are supporters or advocates. While instructors may promote good writing, the sentence emphasizes their evaluative authority, not advocacy. Therefore, this is incorrect.

Blank (ii):
D. self-subverting: Self-subverting means undermining oneself. This fits perfectly since the instructor who assigns a poorly written task is contradicting their own role and weakening their authority, just like a swimming coach who cannot swim.
E. self-aggrandizing: Self-aggrandizing means promoting oneself as important or impressive. This has no connection to the idea of contradiction or incompetence highlighted in the sentence.
F. self-referential: Self-referential means referring to oneself. This is irrelevant to the idea of undermining one’s own authority.