Explanation:

The correct answer is option 'A', which states that the spindle and anvil are the two parts of a Micrometer that are used to hold the specimen. Let's understand why this is the correct answer.

What is a Micrometer?
A micrometer, also known as a micrometer screw gauge, is a precision measuring instrument used to measure the dimensions of small objects with great accuracy. It is commonly used in mechanical engineering, machining, and manufacturing industries.

The Parts of a Micrometer:
A micrometer consists of several parts that work together to provide accurate measurements. The main parts of a micrometer include:

1. Frame: The frame is the main body of the micrometer, which holds all the other parts together.

2. Spindle: The spindle is a cylindrical rod that moves in a parallel direction to the axis of the micrometer. It is used to hold the specimen being measured.

3. Anvil: The anvil is a flat and hardened surface located opposite to the spindle. It is used to support the specimen and provide a reference point for measurement.

4. Barrel: The barrel is the cylindrical tube that houses the spindle and connects it to the frame. It allows the spindle to move smoothly and precisely.

5. Ratchet: The ratchet is a mechanism located on the thimble of the micrometer. It provides a clicking sound and feel when the spindle is being rotated, ensuring consistent and accurate measurements.

Using the Micrometer:
To take a measurement using a micrometer, the following steps are generally followed:

1. Open the micrometer: Rotate the thimble counterclockwise to open the micrometer and create a gap between the spindle and anvil.

2. Place the specimen: Position the specimen between the spindle and anvil, ensuring that it is securely held.

3. Close the micrometer: Rotate the thimble clockwise to close the micrometer and bring the spindle and anvil closer together, applying gentle pressure on the specimen.

4. Take the reading: Read the measurement from the scale on the barrel and the additional scale on the thimble. The reading can be in millimeters or inches, depending on the micrometer.

5. Record the measurement: Record the measurement for further analysis or documentation.

In conclusion, the spindle and anvil are the two parts of a micrometer that are used to hold the specimen being measured. The spindle and anvil provide stability and support to ensure accurate measurements can be taken.