Nancy had to shout to make herself _____ above the sound of the music.[ ]

A. hear

B. hearing

C. heard

D. to be heard

依据给定资料，就警用车辆存在的违规使用问题提出解决措施。
要求：分析条理，观点明确，语言流畅，对策可行。字数不超过350字。