Although plant cells are totipotent, some parts of plants, such as vessel molecules, are dead cells and cannot be selected. Sieve cells have no nucleus and cannot be used as culture materials, so A is wrong. B, the monoclonal antibody obtained by animal fusion technology belongs to cell engineering, and this process does not involve reproduction, so B is wrong; C, urine sugar test paper contains glucose oxidase and catalase, so c is wrong; D auxin has duality, with low concentration promoting growth and high concentration inhibiting growth. Therefore, in order to improve the survival rate of cutting branches, D is correct, because it is soaked with appropriate concentration of auxin.