Which of the following precaution(s) should be observed while using a clinical thermometer?

All of these

The correct answer is option 4. All of these.

Precautions to be observed while using a clinical thermometer

The thermometer should be washed before and after use, preferably with an antiseptic solution.

Ensure that before use the mercury level is below 35°C.

Read the thermometer keeping the level of mercury along the line of sight.

Handle the thermometer with care. If it hits against some hard object, it can break.

Don’t hold the thermometer by the bulb while reading it.