Explanation:

- The phrase "in black and white" means having something documented clearly and unambiguously. It refers to having matters written down on paper to avoid confusion or misunderstanding.

- Option 1: in writing

- This is the correct interpretation of the idiom "in black and white." It means that the contract should be documented formally.

- Option 2: quickly

- This option is inaccurate. "In black and white" does not imply speed or urgency.

- Option 3: in the morning

- This is unrelated to the meaning of the idiom, as it has no reference to time of day.

- Option 4: at night

- This option is incorrect, as the idiom does not pertain to a specific time like night.