② A water molecule consists of one oxygen atom and two hydrogen atoms;

(2) (1) Water is composed of water molecules, and water molecules are composed of oxygen and hydrogen. Water is a metal oxide composed of hydrogen and oxygen, and water molecules are composed of hydrogen atoms and oxygen atoms. The statement about water is correct: water is composed of water molecules, water is a common solvent, water is composed of oxygen and hydrogen, and water molecules are composed of hydrogen atoms and oxygen atoms;

② Activated carbon has adsorption, so its function is adsorption; The function of quartz sand and fluff cotton is to filter out insoluble impurities; There is no need for alcohol lamp and measuring cylinder in the process of purifying water in the laboratory;

③ Hard water produces less foam when it meets soapy water, while soft water produces more foam when it meets soapy water. So soapy water is used to test whether the purified water is hard water or soft water. Hard water is usually softened by heating and boiling in life.

④ According to the number and type of atoms in chemical reaction, it is judged that substance X is chlorine dioxide;

⑤ a. Industrial wastewater contains pollutants such as acid, alkali and heavy metals, and direct discharge will pollute the water body, so a is wrong.

B the waste gas containing SO2 and NO2 will form acid rain, which will pollute the water body after flowing into the river. After treatment, it is discharged to avoid water pollution, so it is correct.

C. The discharge of phosphorus-containing washing powder water will cause eutrophication and pollution of water body, which can be avoided by prohibiting the use of phosphorus-containing washing powder, so C is correct.

D. If pesticides and fertilizers are used unreasonably, residues can flow into rivers with water, causing water pollution. If chemical fertilizers and pesticides are used in large quantities, it may pollute the water body, so it is wrong.

⑥ Flushing the toilet with vegetable washing water can save water.

So, the answer is: (1)1c; ②B(2)①A； ② adsorption; Filtering; Alcohol lamp; Measuring cylinder; 3 soapy water; Heating and boiling; ④ Chlorine dioxide; 3; ⑤ AD ⑤ One water is multi-purpose (or vegetable washing water is used to water flowers, etc. )