Answer:
C. Gaurd rail.
Explanation:
If you have ever moved up and down a staircase, you should probably have encountered a banister. A staircase typically has a handrail(banister) on its sides where you can put your hand as you go up or down on it. A gaurd rail is similar to a banister in that it is also a barrier along the open sides of stairways and platforms. But while a banister (or handrail) is just to give users something to grasp (maybe for balance or rest), a guard rail majorly helps to prevent falling off the stairway.
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