1. I'm sorry that... [ex. I was so rude yesterday] 2. It's my fault. (= I am taking responsibility for the problem) 3. Oops, sorry. (for very small problems) 4. I should have... [ex. called you and told you I'd be late] 5. (formal) I apologize for... [ex. the delay]
Generally speaking, the faculty in most of the engineering institutions are not typically oriented to guide the students to qualify GATE, because of lack of time And expertise. In such a scenario, coaching centers can be especially useful since they have expert faculty, oriented towards GATE preparation.