Analysis of test questions: A. Pay attention to "left object and right code" when weighing solid drugs with tray balance, and the operation in Figure A is wrong;

B, when using powdered drugs, first put the test tube horizontally, use a paper slot or spoon for powdered drugs to send the drugs to the bottom of the test tube, and slowly erect the test tube, as shown in Figure B, the operation is correct;

C. When dropping liquid medicine into the test tube with a rubber-tipped dropper, the dropper should be hung directly above the test tube mouth, and it should not reach into the test tube mouth or touch the test tube wall to prevent the reagent from being contaminated, as shown in Figure C;

D, when measuring a certain volume of liquid with a measuring cylinder, the line of sight should be kept level with the lowest part of the liquid level, and the operation in Figure D is wrong;

So choose B.

Comments: This question mainly examines the weighing, measuring and taking of solid drugs and liquid drugs.