I am confused about the usage of preposition in this sentence:
"They work hard ____ the field everyday".
What should fill the blank?
The correct preposition here is in.
In cases like this, the field is a place or location, so the preposition is in.
He works in a bakery.
She works in a bank.
They work in a bookshop.
When the object in the sentence is an object (a thing), then the preposition would be on.
He works on computers.
She works on innovative projects.
They work on improving performance.