Play: Acts::

To figure out a similar pair, we first need to understand the pair already present.

The relationship between a play and its acts is that a play is divided into acts that together form the whole play. 

Similarly, a novel is divided into chapters that make up the complete novel. Hence, it is a similar pair.

Why not others:

Essay: topics- an essay is not divided into various topics; an essay is written on a single topic.

Game: players- a game is not divided into players, and players are not what form a game.

Poem: rhymes- rhyme is a literary style of poems; rhymes do not form a poem; stanzas form a poem.