Please answer related questions after reading: Gulangyu Island is building the first "recycling" island in China, with zero domestic sewage and domestic garbage.

(1) According to the meaning of the question, the main environmental pollutants on Gulangyu Island come from human domestic garbage, so the main environmental pollutants on Gulangyu Island come from: domestic garbage of tourists; Dead-branch weeds; Therefore, fill in: domestic garbage of tourists; Dead-branch weeds;

(2) According to the meaning of the question, reclaimed water refers to domestic sewage after advanced treatment, and its water quality is between tap water and sewage discharged into the pipeline; After adding soapy water to hard water, less foam is produced, and after adding soapy water to soft water, more foam is produced, so soapy water can be used to test whether "reclaimed water" belongs to hard water; Therefore, the quality of domestic sewage after advanced treatment is between tap water and sewage discharged into the pipeline; Add soapy water, stir, hard water produces less foam, otherwise it is soft water;

(3) According to the meaning of the question: recyclable garbage includes: paper, metal, plastic, etc. Waste newspapers belong to paper, cans and rusty nails belong to metal materials, and mineral water bottles belong to plastic; Rotten apples belong to non-recyclable garbage; The correction liquid bottle belongs to hazardous waste; Therefore: ABCD；; e； f；

(4) From the point of view of protecting water resources, it is possible to prohibit phosphorus-containing washing powder, domestic sewage and industrial sewage from discharging up to standard. So fill in: ① Prohibit phosphorus-containing washing powder; ② Domestic sewage and industrial sewage should meet the discharge standards.