In each of the questions given below four words are given in bold. These four words may or may not be in their correct position. The sentence is then followed by options with the correct combination of words that should replace each other in order to make the sentence grammatically and contextually correct. Find the correct combination of the words that should interchange. If the sentence is correct as it is then, select option “No interchange required” as your choice.

The spinster (A) carefully loosened her thread (B) from the spin (C) and began to spool (D) it into a masterpiece.

To determine the correct combination of words that need to be interchanged, let us analyze the sentence contextually and grammatically:

The original sentence is:
"The spinster (A) carefully loosened her thread (B) from the spin (C) and began to spool (D) it into a masterpiece."

Let us examine the words in bold:
1. spinster (A): A noun referring to an unmarried woman, historically associated with spinning thread. Its placement as the subject of the sentence is grammatically and contextually correct.
2. thread (B): A noun referring to the strand of fiber. Loosening her thread is contextually logical, so (B) is in the correct position.
3. spin (C): A verb or a noun representing a rapid turning motion. In the phrase "from the spin", "spin" acts as a noun, but it does not fit contextually as an object from which thread is loosened or wound.
4. spool (D): A noun representing a cylindrical device on which thread is wound, or a verb meaning to wind magnetic tape or thread onto a spool. In the phrase "began to spool it", "spool" is used as a verb.

If we swap spin (C) and spool (D):
- "from the spool (D)" becomes a highly appropriate noun phrase representing the physical object holding the thread.
- "began to spin (C) it into a masterpiece" becomes a grammatically correct verb phrase, as "spin" means to draw out and twist fibers into thread or yarn, creating a masterpiece.

Therefore, interchanging words (C) and (D) makes the sentence grammatically and contextually correct:
"The spinster (A) carefully loosened her thread (B) from the spool (D) and began to spin (C) it into a masterpiece."

Thus, the correct option is C-D.