Advertising will make everyone happy because it helps people select the best items for them.
Student or Learner
I have one conclusion sentence and the grammar is wrong, but I don't know where. Could you please help me?
Advertising will make everyone happy because it tells people what are the best things to use and save their selecting time.
If only advertising actually did that! Advertising simply makes people want stuff, whether it's the best thing for them or not.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.