## Answer :

**Explanation:**

To find the diameter of the sphere using the given vernier callipers, we need to consider the zero error. In this case, the zero error is 0.9 mm.

Since the vernier scale has a value of 10 Vernier Scale Divisions (VSD) equal to 9 Main Scale Divisions (MSD), we can calculate the correct reading by subtracting the zero error from the Vernier Scale reading.

Let's look at the options:

(a) 2.15 cm: To convert to mm, it would be 21.5 mm.

(b) 2.33 cm: To convert to mm, it would be 23.3 mm.

(c) 2.20 cm: To convert to mm, it would be 22 mm.

(d) 2.24 cm: To convert to mm, it would be 22.4 mm.

Considering the zero error of 0.9 mm, the correct reading would be 22.4 mm - 0.9 mm = 21.5 mm.

So, the diameter of the sphere being measured is (a) 2.15 cm.

Let me know if you have any more questions!