Participles are verb forms which look like verbs + suffix -ing. So having that in mind, the participle in the sentence above is the word standing.
Participles function either as adverbs (when they modify verbs), or as adjectives (when they modify nouns). In this case, the participle acts as an adjective, modifying the word child.
Take off your shoes
No eating in the living room/ tv room
No eating in your beds
Answer is C) that people should not simple stand by and let injustice occur.
