Hi. I searched for this, but couldn't see any advice which dealt with the precise problem. I thought my grammar was reasonable, but then I wanted to put this on the cover of a book: "...everyone needs to watch their back." I stared at it long and hard and then changed it to "...everyone needs to watch their backs." Then I went for "...everyone needs to watch his back." Then I headed for the beer in the fridge. I think both the first one and the third one are correct, although I find the latter maybe a bit too correct. Any comments? Any way around it (it is a strapline, so it needs to sound snappy)? Thanks.