( ): The natural coiled conformation of two complementary, antiparallel DNA chains.

Alan has got ________ with a new computer game recently and spent all days and nights hanging on the Internet, which greatly annoys his parents. A: coiled in B: coiling on C: coiled up D: coiling at

The roof of the residential building was constructed in August. The waterproof coiled material was paved during the day. It was found that the waterproof coiled material was bulging and leaking during the acceptance after the construction. Explain the causes of the above engineering problems.