Explanation:

- Option 1 (a): "Sohan together with" - This part is grammatically correct and refers to Sohan and his friends as a group.

- Option 2 (b): "his friends has" - This is incorrect. With compound subjects connected by "together with," the verb should agree with the first subject, "Sohan," but the entire phrase functions as a plural subject. "have" should be used instead of "has."

- Option 3 (c): "come to the party." - This part is fine. The phrase correctly states the action.

- Option 4 (d): "no error" - This option is incorrect since there is an error in option 2.

Correct Answer: Option 4