Final answer:
In radio communications, the 10 code for stop transmitting is usually 10-7.
Step-by-step explanation:
The 10 code for stop transmitting is not related to scientific notation or any specific mathematical expression. In this context, 10 code refers to a system of numeric codes used in radio communications to convey specific messages or instructions. The code for stop transmitting in this system is usually communicated as 10-7. Therefore, the correct answer is option c), 10^-7.