The question asks which part of the sewing machine is responsible for holding the thread spool. To solve this, let's analyze the given options and identify the correct component:
- Bobbin case: The bobbin case holds the bobbin, which is a small spool-like component that provides the bottom thread in the stitching process. It is situated beneath the needle plate and does not hold the main thread spool.
- Needle plate: The needle plate is a flat metal piece located under the needle and presser foot. It has a hole for the needle to pass through and markings for stitching guidance, but it does not hold any thread spool.
- Spool pin: This is the correct answer. The spool pin is a vertical or horizontal pin on the sewing machine that holds the thread spool. It allows the thread to unwind smoothly as the sewing process is in progress.
- Presser foot: The presser foot is a component that holds the fabric in place as the needle and feed dogs move through the fabric. It does not have any function related to holding the thread spool.
Hence, the correct answer is Spool pin.