Answer:
Answer b) is correct: the tropics are 25N and 25S, and the tilt is 25° for Mars.
Explanation:
The definition of the Arctic Circle is the circumference containing the area where, in the northern's summer solstice, it is wholly sunlit, while it is wholly dark (not reached by sunlight) in northern's winter solstice. (This reasoning may be followed for the Antarctic circle and the southern's summer and winter, by means of an analogy).
The existence of Arctic (and Antarctic) Circle is due to the planet's axis's tilt with respect to its revolution plane around the central objetc, i.e., our common Sun. The angular distance of the Arctic Circle from martian's geographic North Pole is the same as Mars tilt value. So, if the Arctic Circle is located 65° North, that means it is 65° away from the equator, and 90°-65° = 25° from the North Pole. This variable, called co-latitude, is complementary to the latitude (being 90° the sum of these two values, always).
So, the tilt value must be 25 degrees, which in turn means that the tropics must be at that same angular distance from the equator, both North and South. So the tropics are 25N and 25S. Answer b) is correct.
