Figure 1 shows the configuration of main scale and Vernier scale before measurement. Fig. 2 shows the configuration corresponding to the measurement of diameter 𝐷 of a tube. The measured value of 𝐷 is:

Fig. 2

To find the diameter $D$ of the tube, we first determine the least count of the Vernier caliper and then read the scale configurations from the provided figures.

Step 1: Find the value of one Main Scale Division (MSD)
From Figure 1, the main scale has 10 divisions between 0 and 1 cm. Therefore, the value of one main scale division is:
$1\text{MSD}=\frac{1\text{cm}}{10}=0.1\text{cm}$

Step 2: Determine the Least Count (LC) of the Vernier caliper
Figure 1 shows the configuration before measurement (with jaws closed). The 10 divisions of the Vernier scale coincide exactly with 9 divisions of the main scale (up to 0.9 cm).
$10\text{VSD}=9\text{MSD}$
$1\text{VSD}=0.9\text{MSD}$
The Least Count (LC) is given by:
$\text{LC}=1\text{MSD}-1\text{VSD}=1\text{MSD}-0.9\text{MSD}=0.1\text{MSD}$
Substituting the value of 1 MSD:
$\text{LC}=0.1\times 0.1\text{cm}=0.01\text{cm}$
Additionally, since the zero marks of both the main scale and the Vernier scale align perfectly in Figure 1, there is no zero error.

Step 3: Read the values during measurement from Figure 2
- Main Scale Reading (MSR): In Figure 2, the zero mark of the Vernier scale lies between the 0.1 cm and 0.2 cm marks of the main scale. Thus, we take the lower value as the main scale reading:
$\text{MSR}=0.1\text{cm}$
- Vernier Scale Reading (VSR): We look for the division on the Vernier scale that aligns perfectly with any division on the main scale. By observing Figure 2, the 3rd division of the Vernier scale aligns exactly with the 0.4 cm mark of the main scale.
$n=3$

Step 4: Calculate the measured diameter $D$
The formula for the total reading is:
$D=\text{MSR}+(n\times \text{LC})$
Substituting the values:
$D=0.1\text{cm}+(3\times 0.01\text{cm})$
$D=0.1\text{cm}+0.03\text{cm}=0.13\text{cm}$

Therefore, the measured diameter of the tube is 0.13 cm, which corresponds to the third option.