Question

necesito el termómetro porque pienso que tengo
un hueso roto
dolor de estómago
una fiebre
dolor de cabeza

Explanation:

A thermometer is used to measure body temperature. A fever (una fiebre) is indicated by an elevated body temperature, which is what a thermometer detects. A broken bone (un hueso roto) would require an X - ray or physical examination, stomach pain (dolor de estómago) and headache (dolor de cabeza) are symptoms that may not directly relate to temperature measurement.

Answer:

Option 3. una fiebre