The geographical interest group of a domestic school measured the shadow length of the school flagpole at noon in the four solar terms in the table below. See the table below for data records.

Because the earth revolves around the sun, the axis of the earth and the orbital plane form a fixed inclination of 66.5, which makes the direct point of the sun's rays move regularly between the Tropic of Cancer and the Tropic of Cancer in a year, which leads to the change of the height of the sun at noon, that is, the length of the shadow of the flagpole. When it is the summer solstice in the northern hemisphere, the sun shines directly on the tropic of cancer, and the angle of the sun height in the northern hemisphere is the largest and the shadow is the shortest. From winter to the sun, the sun shines directly on the Tropic of Capricorn, and the solar altitude angle in the northern hemisphere is the smallest and the shadow is the longest; At the vernal equinox or autumnal equinox, the sun shines directly at the equator, the solar altitude angle in the northern hemisphere is between the winter solstice and the summer solstice, and the shadow length is between the winter solstice and the summer solstice.

As can be seen from the data in the table, the shadow length of the flagpole is the shortest at time ②, so it can be judged that the sun is on the tropic of cancer, which is the summer solstice in the northern hemisphere.

Therefore, choose: B.