Read the daylight map (the shaded part in the map indicates night)

(1) When reading the picture 1, extreme days appeared in the Arctic Circle and its northern region, which is the earth illumination map of the summer solstice in the northern hemisphere. At this time, the earth is in position B in Figure 2.

(2) The points and places on the same meridian are the same. In figure 1, there are three places, namely B, C and D, which are the same as those in A; From summer to the sun, the noon sun height decreases from the tropic of cancer to the north and south sides, which is the same as the noon sun height in A, and the two points are located on the equator.

(3)A is vernal equinox, and when the earth is located in position A in Figure 2, the length of day and night in Suqian is equal; The latitude distribution law of noon sun height around the world is decreasing from the equator to the north and south sides.

Therefore, the answer is: (1) summer solstice; B.

(2)b； Ding.

(3) The length of day and night is equal; Decreasing from the equator to the north and south sides.