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

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