The filibuster, a parliamentary device that slows the snail’s pace that prevails even in the best of times in congressional sessions and tests the endurance of everyone associated with it, seems more and more an anachronism in the age of telecommunications.

(A) sessions and tests the endurance of everyone associated with it, seems

(B) sessions and tests the endurance of everyone who is associated with it, seeming to be

(C) sessions, tests the endurance of everyone associated with it, seems

(D) sessions, that tests the endurance of everyone associated with it and seems（A）

(E) sessions, testing the endurance of everyone associated with it and seeming

The key is (A), however, I ruled out (A) because that is not used between and and tests. Why there is no that ? is it acceptable to omit that ?

Thanks!