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Which of the following statements regarding the selection of design parameters for rainwater pipelines in residential communities is in line with the current \"Code for Design of Building Water Supply and Drainage\"? ( ) A. The design rainfall duration is taken as 10 minutes. B. The design return period is selected as 5 years. C. The catchment area is calculated based on the horizontal projection area of the ground in the area in question. D. The runoff coefficient is determined by referring to values from nearby areas. Answer: C. The design rainfall duration specified in option A should include both the time it takes for water to collect on the ground and the time it takes for the rainwater to flow through the drainage pipes. According to Article 4.9.4, Paragraph 2 of the current “Code for Design of Building Water Supply and Drainage Systems,” the time required for water to collect on the ground is 5–10 minutes; therefore, option A does not comply with the requirements of the code. Option B does not comply with the provisions of Table 4.9.5 in Article 4.9.5 of the current \"Code for Design of Building Water Supply and Drainage\". The design return period for rainwater pipelines in residential areas is selected as 1–3 years. Option D does not comply with the provisions of Article 4.9.6 of the current Code for Design of Building Water Supply and Drainage. The runoff coefficient of a residential area should be calculated as a weighted average of the runoff coefficients of its various catchment areas. Option C complies with the provisions of Article 4.9.7 of the current Code for Design of Building Water Supply and Drainage.