true or false?

Question

True or false (yes or no, 1 or 0) problems with wrong-answer penalties:
a) 75-ohm cable are used for analog transmission
b) Single-mode fiber are more expensive but are widely used for longer
distances than multi-mode fiber
c) Downlink are always have higher frequency than uplink for satellite
communication
d) We need at least 4 geostationary satellites to cove the whole earth
surface

Answer 1

I know a is true. I can't comment on the rest of them.