theory可数吗?如果可数,怎么变复数啊?急等

　　I looked forward to the exploration of their theories.

　　我期待着对他们的理论进行探讨。

　　Don't let yourself be distracted by fashionable theories.

　　别让自己被新潮的理论给分心了。

　　These theories are now largely discredited among linguists.

　　这些理论现已大多受到语言学家的质疑。

　　I accept his theories, but not without certain qualifications.

　　我接受他的理论，但并非毫无保留。

　　Over the years several similar theories have been put forward.

　　多年来几种类似理论被提了出来。