Item a is correct. This sentence comes from Su Shi's Huanxisha Dragon Boat Festival in the Song Dynasty. The activities described by the author are colorful silk threads and hanging symbols, which are traditional customs of the Dragon Boat Festival.
Item b is correct. This sentence comes from Zhao Lu's Poem of Crossing the River in Tang Dynasty, which describes the official custom of dragon boat race on the Dragon Boat Festival.
Error C, this sentence comes from Wang Changling's "Lotus Picking Two Songs" in Tang Dynasty, which describes the lotus picking activities of girls in water villages and has no obvious relationship with the Dragon Boat Festival.
Item d is correct. This sentence comes from "Watching the Match in the Afternoon" written by Bian Gong in the Ming Dynasty, which depicts the official custom of the Dragon Boat Festival.