B .  
By measuring body temperature using a thermometer
C .  
By checking if the person looks tired and weak
D .  
By checking if the person is eating properly or not
Answer: Option B : B By measuring the body temperature using a thermometer, you can be sure whether a person has fever or not. Normal human body temperature is 98.4 degree fahrenheit. If the thermometer reads above this temperature, this means the person has fever.
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