No matter how frequently ____, the works of Beethoven still attract people all over the world. [ ]

A. performed

B. performing

C. to be performed

D. being performed

构成共同海损的条件有（）。

A、必须是确实遭遇危难

B、必须是自然灾害造成的损失

C、必须是有意的、合理的措施造成的损失

D、必须是为船、货共同安全而采取的措施

E、必须是属于非常性质的损失