[单选题]
A convex lens has a focal la- q1nu3a j1bfength g 9n.:zmb z5ivdbhv 7/$f$. An object is placed between infinity and $2f$ from the lens on its axis. The image formed is located
A. at $2f$.
B. between $f$ and $2f$.
C. at $f$.
D. between the lens and $f$.
