What role did the roman empire and christianity play in the creation of the modern gregorian calendar?

Around the third week of a college class, a professor decides she’s had enough, is tired of dealing with bureaucracies, and wants out. so one day, instead of coming to class, she flies to tahiti and sells souvenirs on the beach. if this happened, the college would simply assign a substitute to finish the course. what does this tell you about the nature of the authority wielded by a professor?

Population parameters are difficult to calculate due to

Most of the workers who laid the central pacific railroad were?