Final answer:
The first thing you key when keying a personal-business letter is the date. Option b.
Step-by-step explanation:
The first thing you key when keying a personal-business letter is the Date. The date should be written out in the proper format, including the month, day, and year. For example, if today is January 1, 2022, you would write 'January 1, 2022'.
After keying the date, you would proceed to key the sender's address, recipient's address, and salutation. The writer's name is typically included at the end of the letter, after the closing. Option b.