Explanation:

Correct Option 2- Order for a new . This part has error.

- The sentence is divided into parts for error identification:

- (1) "On Diwali I will"

- (2) "order for a new"

- (3) "pair of spectacles"

- (4) "no error"

- Option 1, a: No error in this part. It correctly introduces the time and intention.

- Option 2, b: Incorrect usage. It should be "order a new pair of spectacles" without "for."

- Correct Answer: Option 2, b

- Option 3, c: Correctly uses "pair of spectacles" for more than one lens.

- Option 4, d: Marks the absence of errors, but there is an error in Option 2.