Fluidos que intervienen en la elaboración del hormigón

The last one, because there is the same number of atoms (p, cl, h, and o) on both sides of the reaction.

Because if a good speech is delivered badly it can bore the audience, confuse them, or make them distrust the speakeri think they all come back to this one, except that last answer because that is false. if your audience starts making fun of you or gets distracted it is because they are either bored, confused or distrust you.