Student or Learner
Can I say "Close the bottle tightly, or it'll be flat."
I know that "it'll go flat" is right but I was wondering if "it'll be flat" is also right.
Thanks in advance.
As it takes some time for a drink to go flat after its bottle has not been closed properly, we use the future tense 'it will go flat'. You could say 'it will become flat', but not 'it will be flat', as this suggests that the drink will be flat as soon as the bottle is closed.
I hope this helps!