Answer: A search engine uses machines to index webpages; a gateway is compiled by experts or librarians. ... A search engine is simpler to use; a gateway requires the searcher to use scientific terms. A search engine is free; a gateway requires payment for the subscription to the service.
Anuther word for opinion could be a response
The second option because it uses proper tense (past tense), the rest do not make sense it mixes the tenses (past, current, future).
They are fighting for a person that they trust and not for the opposite side.