.He suddenly saw what looked like a snake in the darkness. For an instant his heart seemed to stop ______.

A．to beat

B．beating

C．beaten

D．being beaten

创造性是科研工作者选题时应遵循的基本原则之一，其含义包括（）

A.先进性

B.新颖性

C.独创性

D.突破性

E.以上都是