The _ is the individual or group that develops the message to be communicated to internal and external parties:

Answer ___________________ a)

..........................a. source.

 a. >>>>>>>>>>>>>>>> source.

the source should be the correct answer

answer A ___________________________________

The answer is :Option ( A )

.................. a. source...................

Agree with professionals..... 

My answer is same as other experts, which is option (A)

Option -----------------------A

Thanks