This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to check vitals
Pick a thermometer.
To take someone's temperature, you have several options when it comes to thermometers. Glass or digital thermometers can be used orally, rectally, and under the armpit.

[1]. Special thermometers can be used on the forehead (skin) or in the ear. For babies under 3 months, always use a digital or glass thermometer to take a rectal reading.
[2]. These thermometers remove length, as well as read the actual measurement. Digital thermometers will instead make a radial reading.
[3]. Thermometers regulate a person's body temperature and should be taken professionally and carefully. Digital thermometers can take different lengths depending on the intended recipient's body temperature.
[4]. Digital thermometers are the most common and are primarily used to measure body temperature, but you can also use them to measure other body temperature issues. Take your temperature directly from your genitals.
The answer is:
[1].