Which of the following describes a known dividend yield on a stock?

Question $8$ options:

a$)$

Dividends will yield a certain return to a person buying the stock today

b$)$

Dividends per year as a percentage of the stock price at the time when dividends are paid are known

c$)$

The size of the dividend payments each year is known

d$)$

Dividends per year as a percentage of today's stock price are known