Which is "correct": Everybody should open their MOUTH when they see injustice./ Everybody should open their MOUTHS when they see injustice. Thank you.
Well, you've just raised one of the stickiest problems in English grammar. I see it almost everyday. According to standard grammar, as I understand it, neither of these sentences is correct. Everybody is singular and requires a singular pronoun. Hence, you would have to say, "Everybody should open his mouth when he sees injustice." After all, you can't say "Everybody are here," so clearly everybody requires a singular verb and singular possessive pronoun.
That is what we read in on sites such as
this, or, more definitively,
this.
There is a problem with this, though. How do we avoid the continual use of the male pronoun? Do we write the ugly, "Everybody should open his/her mouth when he/she sees injustice"? Or should we simply alternate, using his one time and her the next?
The other problem is that we will frequently hear a sentence such as, "Everybody (or everyone) was standing around with their mouths open." Maybe this sounded funny once, but does it really bother people today? We picture the crowd of people and clearly there are multiple mouths.
The result is that I am confused. Generally I encourage students to avoid such constructions by finding another way to say it. But I would be eager to hear what others have to say about this knotty (and, for me, confusing) issue.
Thanks for bringing it up.