(20 12? Yiwu) is the experimental device of the research-based learning project "Study on the Conservation of Mass in Chemical Reactions" in the second volume of Grade 8. The experiment passed the test. (1) According to the function of each knob in the device, the knob that can adjust the inclination of the test tube is B;

(1) a. According to the solubility of oxygen, oxygen is insoluble in water and kerosene. Adding some kerosene to the measuring cylinder can reduce the dissolution of oxygen in water, so a is correct;

B, plastic nozzle spray continuous uniform bubbles, the collected gas is pure oxygen, but the collected gas is less, does not conform to the law of conservation of mass, so b is not correct;

C, the mass of mercury oxide reduced by thermal decomposition is the mass of collected oxygen. Therefore, stopping heating before the complete decomposition of mercury oxide has no effect on the experimental results. So, C is correct.

So, the answer is: (1) b; (2) alternating current.