The correct answer is Option 4 i.e 4 No error Key Points Looking at the above sentence we find that: The sentence does not have any error as it is contextually and grammatically correct. Hence the correct answer is Option 4. Mistake Points In the sentence in part 1 looked at might seem wrong and looked for might seem appropriate. However, we should keep in mind that both looked at and looked for have contextual differences. Here looked at implies that the predictive factors were already existing and they looked at it. If it is changed to looked for it implies that the predictive factors were not existing and they had to look for it. This changes the context of the sentence, even though it sounds correct. Important Points We use whether and not if before a to-infinitive, often when we're referring to future plans or decisions For e.g.-I was wondering whether to go for a class.