In the following question, a sentence is divided into few parts. Rearrange these parts and identify the correct sequence making the sentence grammatically and contextually correct.

(A) for improving

(B) student discipline

(C) announced a new policy

(D) the school principal

To find the correct sequence that forms a grammatically correct and contextually meaningful sentence, let us analyze the roles of each part:

- (D) the school principal acts as the subject of the sentence.
- (C) announced a new policy acts as the verb phrase/action taken by the subject (the school principal). Putting (D) and (C) together gives: "the school principal announced a new policy".
- (A) for improving introduces the purpose of the new policy.
- (B) student discipline is the object of the prepositional phrase starting with "improving". Connecting (A) and (B) gives: "for improving student discipline".

Combining all these parts in the order of D → C → A → B, we get:
"The school principal announced a new policy for improving student discipline."

This sentence is grammatically complete, logical, and contextually correct. Therefore, the correct sequence is DCAB.