What does the idiom 'Hit the nail on the head' mean?

What does the idiom 'Break the ice' mean?

Choose the correctly corrected sentence: 'She don't know the answer.'

What does the idiom 'Once in a blue moon' mean?

Choose the correctly corrected sentence: 'He is working here since 2018.'

What does the idiom 'Bite the bullet' mean?

Choose the correctly corrected sentence: 'Between you and I, this is wrong.'

What does the idiom 'A blessing in disguise' mean?

Choose the correctly corrected sentence: 'Everyone have submitted their assignment.'

What does the idiom 'Burn the midnight oil' mean?

Choose the correctly corrected sentence: 'I am living in Lahore since ten years.'