ANSWER is option 3) i.e. C. Explanation:Conditional sentences are statements discussing known FACTORS or hypothetical situations and their consequences.One of the structures is mentioned below:This particular type is followed when something didn't happen as a certain condition wasn't fulfilled.If + Past PERFECT, Subject + Would have + V3 + Object.For example:If I had noticed you, I would had call you. If I had noticed you, I would have called you. Hence in the 3rd part of the given sentence, 'would have' will be used INSTEAD of 'will have'.Correct Sentence: " If I had known this earlier I would have helped him."