Helen had to shout _____ above the sound of the music. [ ]

A. making herself hear

B. to make herself hear

C. making herself heard

D. to make herself heard

采用分开式扣件的木枕线路、道岔，如无爬行时，可不安装防爬设备。在混凝土枕线路上，采用的是弹性扣件，也可不安装防爬设备。