Different kinds of signals are

A. Mechanical, Thermal मैकेनिकल, थर्मल

B. Magnetic, Electric मैग्नेटिक,इलेक्ट्रिक

C. Chemical, Radiation केमिकल,रैडिएशन

D. All of the above ऊपर के सभी

Correct Answer is :

D. All of the above