Final answer:
The missing step in the transmission sequence is that radio waves are amplified and demodulated before the final step where a signal is heard, seen, or used.
Step-by-step explanation:
The correct missing step in Karl's sequence of steps for transmitting information via electromagnetic waves is: Before step 5, radio waves are amplified and demodulated. This is because, after the antenna captures the modulated waves, the radio or television amplifies the weak signal that it receives and then demodulates it, meaning it converts the radio frequency signal back into a form that represents the original information, which can be audio and/or video. The process of demodulation decodes the amplitude, frequency, or phase variations that contain the conveyed information. Only after these steps can a signal be heard, seen, or used (step 5).