comment box: the mistake of MISS MUFFET

FACEBOOK REALITY # 1

one comment: ARE THIS CELLPHONE ALL YOURS?

the grammar, the subject-verb relations s just too mara and clara (fighting characters in philippine TV drama) that is why, my hackles raised and instantly i corrected the student (her name is _________) but not in the comment box but i sent some private letter. 
here's the excerpts--

  me(frets obviously): Ms Muffet pls change ur comment. ur grammar is wrong.

ms muffet: sori, sir!

me: dont say sorry. now, delete it...

ms muffet: OK.

me: change this (demonstrative pronoun, for singular form)to these BECAUSE there are soooo many celfones and pls, add s to ur celfones because there many celfones!

diagram to this lesson?

are all this these celfone celfones (with s, this time)yours?