Is the process of translating a message received into understandable language or symbols.
a. encoding
b. decoding
c. observation
d. communication

Option B

Explanation:

The process of converting a message into a form where it can be transmitted as signals from the sender to the receiver is called as encoding. However, the process of the reconverting the encoded message into intelligible forms so that a receiver could understand the message is called as decoding. However, the entire process of encoding and decoding is known as communication.  

For example -  

In order to decode a sound signals, analogue from digital are retrieved.  

Hence, option B is correct

energy and particles