I would like to get an if function that will display the bold item and need help writing it could someone help me out

here is a basic example of what I am looking for, I want the bolded text in column B to continue on each line item in column A until the next bolded text in column B

A B
Dog Dog
Dog 1.00
Dog 2.00
Dog 3.00
Cat Cat
Cat 1.00
Cat 2.00

let me know if you would be able to help me create this