Answer:
protest
Step-by-step explanation:
Prepositions are linking words which express how the different elements in a sentence or clause are related. Examples of prepositions are at, on, in, upon, by and of.
In the sentence given, the preposition by means of means through or by virtue of. Besides, the object of the preposition is usually the noun, person or thing which follows it and which is its recipent, such as protest.