A plot of sunrise position as a function of time of the year looks like the following: a) straight line B) parabola C) wave D) inverse line

B) Parabola

Explanation: The function sunrise can be seen as the function

F (t = day of the year) = hour of the day when the sun appears.

There are two important days in a year: - 21 of July, the summer solstice, and, - 21 of December, the winter solstice.

The 21 of July is the day of the year when the sun appears the earliest, and, the 21 of December is the day of the year when the sun appears the latest.

We measure the sunrise in on year, i. e, 366 days, we begin to measure the 21 of December and end our measurements the 21 of December of the next year. Hence, t=0 corresponds to the 21 of December, t=366 corresponds to the 21 of December of the next year and t_mid=366/2 corresponds to the 21 of July.

It holds that F (0) = F (366) is the minimum of the function and F (t_mid) is the maximum of the function. Between t=0 and t_mid F (t) is decreasing, also between t_mid and t=366 F (t) is increasing. Moreover, by the way that the earth travels around the sun, we can assume that F (t) is symmetric with respect to t_mid. Finally, by plotting or drawing F (t), for t between 0 and 366, looks like a parabola facing downwards.