Student or Learner
Which preposition are we supposed to use in this case, please? :
-We must keep control on /over the quality of our products.
Thanks a lot
I'd say "keep control of" but in your sentence, I'd just say " We must control the quality" and leave "keep" out of it.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.