Which of these statements accurately explains why the common era begins with the birth of jesus of nazareth over 2,000 years ago?

a. jesus instructed his christian followers to create a new calendar based on his birth and spread it to every country throughout the world.

b. the period of time now described as the common era officially began with jesus's declaration that christians, muslims, and jews have many beliefs in common.

c. jesus developed a system of measuring time that could be used to more accurately track the passage of time than any other culture's calendar.

d. the period of time now described as the common era is based on older christian periodization that divided time into a period before jesus's birth and a period afterward.