Here’s the identification of mistakes in each sentence:

**24. He sat (A) by the phone (B), wish (C) it would (D) ring.**
Mistake: (C) "wish" should be "wishing."
Corrected: He sat by the phone, wishing it would ring.

**25. Did (A) she used (B) to have (C) long hair (D)?**
Mistake: (B) "used" should be "use."
Corrected: Did she use to have long hair?

**26. We are in compete (A) with four (B) other companies for (C) the contract (D).**
Mistake: (A) "compete" should be "competition."
Corrected: We are in competition with four other companies for the contract.

**27. I find (A) it’s hard (B) to walk now (C). I’ve been bare (D) my feet all day.**
Mistake: (D) "bare" should be "baring."
Corrected: I find it’s hard to walk now. I’ve been baring my feet all day.

**28. The centre offers (A) activities for (B) everyone, whatever (C) your age or mental (D).**
Mistake: (D) "mental" should be "mentality."
Corrected: The centre offers activities for everyone, whatever your age or mentality. (Note: "mental well-being" may also be acceptable depending on the intended meaning.)