There is a new park near Andy’s home. It’s fine today. Andy and his family are in the park now. On their left, there is a café. On their right, there is a big lake. There are many flowers and trees around the lake. There’s a small hill behind the lake. Near the lake, there are two signs. One says, “Don’t swim in the lake!” The other says, “No fishing!” But you can go boating on the lake. There is a beautiful garden in the middle of the park. There are green grass and beautiful flowers in it. There are some small shops between the lake and the garden. The park is so nice. Andy and his family like it very much.

如图,AB是⊙O的直径,弦CD⊥AB,垂足为E,如果AB=20,CD=16,"那么线段OE的长为（）