English passive and Spanish active voices
My study and learning: I had no idea I was getting into studying the English passive sentence structure. I have learned two things must occur to have an English passive sentence:
-- 1 -- there must be the verb construction "to be" + past participle
-- 2 -- the verb must be transitive which means the verb must have an object (direct or indirect)
To speak fluently in Spanish they do not use the Spanish passive sentence structure very often. The English passive sentence can be changed to a Spanish active sentence in two ways:
-- 1 -- Make the sentence active in Spanish. An example: The book was bought by Robert -- Roberto compró el libro.
-- 2 -- Use a reflexive verb or "passive se". An example: Apples are sold here -- Se venden manzanas aquí.
¨....se necesita el conocimiento, también,¨ is more fluent Spanish and more easily understood by a native speaker, and now known to me as the ¨passive se¨ in Spanish.
With your comments and the link I have a better understanding of these sentence structures and I wish to thank you all, Jeska, mcl020, farallon7, Jasmine101, xocoyote y Paralee! I don´t have it fully but with time, patience and more practice I hope I will.

1 Answer
Great info, Bandit. Thanks for posting this!