The voltage ranges for a logic high and a logic low in RS-$232$ C standard is
ans is (c)
The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are either in the range of +3 to +15 volts or the range −3 to −15 volts
https://en.wikipedia.org/wiki/RS-232
http://www.lammertbies.nl/comm/info/RS-232_specs.html
Option B