The word, 'Monday' is the name of a week. As it is a proper name, the letter 'm' has to be capitalised. In options C and D, the letter 'm' is not capitalised.
The correct way of representing time is: 7 o'clock. In options B, C and D, the time is incorrectly represented. In option B, the apostrophe is incorrectly placed. Further, there is no space between the letter 'o' and 'clock'. In option D, the letter 'O' is capitalised, which is incorrect.
The only option with no errors is option A, which is the correct answer.