| A |
| This question is about the common instruments and the basic operation of chemical experiments. A, access to solid medicines, first of all, the test tube should be placed horizontally, with a paper slot or medicine spoon to the bottom of the test tube, so the operation shown in the diagram is wrong; B, access to liquids: ① reagent bottles bottles should be tightly next to the mouth of the test tube, to prevent liquid flow; ② labels toward the palm of the hand, to prevent liquid flow corrosion of labels; ③ corks are not placed upside down on the table, may be contaminated with the stopper, and thus contaminated with the medicine, the diagram shows that operation Correct; C, in the test device tightness, the use of the device is to change the pressure of the gas, there are bubbles, indicating that the device is good airtight, otherwise airtight is not good, the operation is correct, it is correct; D, to the liquid heating, the liquid in the test tube can not be more than the volume of the test tube 1 / 3, to prevent the boiling splash, so the operation is correct. Therefore, the choice of A |