Directions: In the statement below, four words are marked as (A), (B), (C), and (D). These words may not be in their correct positions. Select the option that gives the correct pair(s) of words that must be interchanged to make the sentence grammatically correct and meaningful.

Exercising meticulous care (A) while reckoned (B) the raw canvas, the painter sketching (C) that this artwork would become his grandest masterpiece (D) yet.

The correct option is Only (B)-(C).

Explanation:
Let us analyze the original sentence:
"Exercising meticulous care (A) while reckoned (B) the raw canvas, the painter sketching (C) that this artwork would become his grandest masterpiece (D) yet."

In the given sentence structure:
1. Word (B) "reckoned" is improperly placed after the conjunction "while". A present participle verb (ending in -ing) like "sketching" is required to describe the ongoing action performed on the raw canvas.
2. Word (C) "sketching" is incorrectly placed as the predicate verb following the subject "the painter". The sentence requires a main finite past-tense verb to complete the clause.

By interchanging words (B) and (C), the sentence reads:
"Exercising meticulous care (A) while sketching (B) the raw canvas, the painter reckoned (C) that this artwork would become his grandest masterpiece (D) yet."

This replacement makes the sentence grammatically correct and contextually meaningful:
- "while sketching the raw canvas" appropriately describes the action being carried out.
- "the painter reckoned" correctly uses "reckoned" as the past-tense verb meaning thought or considered.

Thus, the correct pair of words to be interchanged is (B)-(C).