—Have you finished the work?

—Not yet, but no matter how hard it is, we'll keep _____ until we make it.[ ]

A. failed

B. trying

C. tried

D. failing

有动车组停靠或通过的车站，应当对跨线候车室窗户或天桥进行封闭管理并有“禁止抛物”等相应的安全提示。