There are different methods that you can use but the most effective one has to follow a certain process in order to reach the maximum level of effectiveness. There is a need to increase the antennas in both the receiver antenna area and the transmitter side. This means that E and F are good options if you want to improve the transmission.
Do not underestimate the other methods that are available too. Even A, D, and G will also be very effective for your needs. What do you think will be the most ideal method for you? This will depend on your budget and the items that you already have.
Increase signal to noise ratio at the receiver Increase the transmitter power Use multiple antennas at the receiver side (receiver antenna diversity) Use multiple antennas at the transmitter side (beam focusing) Reduce the noise power at the receiver (use advanced receiver RF design)