Which one (s) of the following is or are correct?

A.Isotactic and syndiotactic polymers possess stereo-regular structures

B.Atactic and isotactic polymers possess stereo-regular structures

C.Isotactic and syndiotactic polymers are rigid, crystallizable, high melting, and relatively insoluble

D.Atactic polymers are rigid, crystallizable, high melting, and relatively insoluble

正确答案：Isotactic and syndiotactic polymers possess stereo-regular structures；Isotactic and syndiotactic polymers are rigid, crystallizable, high melting, and relatively insoluble