Why did Mr. Curtain promise to promote Reynie?

The choice indicating that Reynie had been making perfect scores highlights Mr. Curtain's strategy in rewarding Reynie for his academic excellence. Mr. Curtain, who is an antagonist in the story, sees Reynie’s intelligence and achievements as assets that can further his own goals. By promising to promote Reynie based on his perfect scores, Mr. Curtain aims to manipulate him into thinking he is valued, thus securing Reynie's loyalty or compliance. This reflects a calculated move on Mr. Curtain’s part, as he intends to use Reynie’s abilities to serve his own interests, rather than out of true admiration or a desire for collaboration.

In contrast, the other choices do not align with Mr. Curtain's motivations. While Reynie's creativity or personality may be noteworthy traits, they are not the driving reasons for Mr. Curtain’s promise. Additionally, although becoming an assistant might seem appealing, it lacks the direct link to Reynie's academic success, which is the primary factor in Mr. Curtain’s decision.