The answers are C and E.

The sentence contrasts the reception of the author's earlier novels, which contained lyrical digression, with her later works, which were sparse and unornamented yet equally acclaimed. This suggests that critics initially treated lyrical digression as something necessary or expected in serious literary fiction.

A. anomalous
Anomalous means unusual or deviating from the norm. The sentence does not suggest lyrical digression was seen as unusual; rather, it was treated as something important or expected.

B. superfluous
Superfluous means unnecessary. This contradicts the sentence because critics initially seemed to value lyrical digression in serious fiction.

C. indispensable
Indispensable means absolutely necessary. This fits perfectly because the sentence suggests critics initially believed lyrical digression was essential to serious literary fiction.

D. imperious
Imperious means domineering or arrogant. This has no logical connection to the role of lyrical digression in literature.

E. obligatory
Obligatory means required or expected. This also fits perfectly because the sentence implies critics initially viewed lyrical digression as a necessary feature of serious fiction.

F. gratuitous
Gratuitous means unnecessary or unjustified. This is the opposite of the intended meaning.