The longest day in Suzhou is [] A, winter solstice B, summer solstice C, vernal equinox D and autumn equinox.

The longest day in Suzhou is [B ]B, which means that the real summer has arrived and the hottest time of the year is coming. The solstice in summer is the longest day in a year, which is what the old people say today is the longest day.

The solstice in summer is the harvest season of wheat. Since ancient times, people have had the custom of celebrating harvest and offering sacrifices to ancestors at this time in order to pray for a good year. Therefore, the summer solstice, as a festival, was included in the ancient ritual of offering sacrifices to the gods.

In the Zhou dynasty, sacrifices were made to gods from summer solstice, which meant to eliminate famine, hunger and death. The solstice of summer is just after the wheat harvest. Farmers not only thank God for the bumper harvest, but also pray for the "autumn report". Around the summer solstice, some places hold a grand "Summer Wheat Festival", which is the relic of the ancient "Summer Wheat Festival" activities.