18.
Your Answer is
Correct Answer is H
Explanation
occasion means "opportunity", so it must be followed by when to guide the attributive clause, and H is correct.
Item F: for which is wrong, because the semantics of for the occasion is wrong.
G item: which must act as a clause component, and there is no lack of components in the clause here.
Item J: Because occasion is not a location, item J is wrong.