Let R be a ring and let U and V be (two-sided) ideals of R. Which of the following must also be ideals of R ?
I. {u + v : u \in and v \in V}
II. {uv : u \in U and v \in V}
III. {x : x \in U and x \in V}
(A)II only (B)III only (C)I and II only (D)I and III only
D