What is/are the precaution(s) to be taken while reading a laboratory thermometer?

All of these

The correct answer is option 4. All of these.

Let us go through each precaution:

1. The laboratory thermometer should be kept upright, not tilted: This ensures that the mercury (or other liquid) inside the thermometer is uniformly affected by the temperature of the substance being measured. Tilting could cause uneven heating and inaccurate readings.

2. The laboratory thermometer bulb should be surrounded from all sides by the substance of which the temperature is to be measured: Placing the bulb in the center of the substance being measured ensures that the thermometer accurately reflects the temperature of that substance. If the bulb is not surrounded, the reading might be influenced by the surrounding air.

3. The laboratory thermometer bulb should not touch the surface of the container: This prevents the transfer of heat directly from the container to the bulb, which could affect the thermometer's accuracy. The bulb should be immersed in the substance but not in direct contact with the container.

By following these precautions, you ensure that the laboratory thermometer provides an accurate representation of the temperature of the substance being measured.