Thermosphere , Stratosphere , Exosphere , Ionospher , Troposphere - Choose Odd Word

Choose or find odd word

Thermosphere , Stratosphere , Exosphere , Ionospher , Troposphere

A. Thermosphere

B. Stratosphere

C. Exosphere

D. Ionospher

E. Troposphere

Answer: A . Thermosphere

Justification: All except Thermosphere are layers of atmosphere.