Respuesta :
The option that best describes the word 'adorn' as it is used in the sentence is B) to decorate.
'Adorn' means to add ornaments to a thing in order to enhance its appearance and make it more attractive. In this case, the thing that is being decorated is the bridge. Moreover, in this sentence, the sentinels are equated to ornaments because they are standing still near the stream as if they were statues adorning the bridge.