Hi!
So if the exchange rate between the dollar and the yen changed from 120 yen to 1 dollar to 118 yen to 1 dollar, then that means it depreciated against the yen. The reason is because it fell in value; it took less yen to get a dollar, and you get less yen when you give a dollar.
Therefore, imports from Japan became more expensive as you would have to pay more US dollars to get the same amount of yen.
So your answer is C.
Hope this helped!