Question

____you work hard,you will fail in the examination. fill suitable conjunction

Answer 1

'Unless' is the right answer.
'if' will come only when 'pass' comes in place of 'fail'

Answer 2

Unless you work hard, you will fail in the examination.

‘Unless’ is the suitable conjunction used here, to tell that the person needs to work hard for avoiding failure in the examination.

A conjunction is used to join two different sentences by inducing a definite meaning, so that it becomes a single meaningful sentence.