On frequency
Select the correct readback.
Why exact readbacks matter
What must always be read back
Per the FAA Aeronautical Information Manual (4-4-7) and Order 7110.65, certain items must be read back verbatim: runway hold-short instructions, runway crossing clearances, takeoff and landing clearances, and any altimeter setting assigned. A generic "Roger" or "Wilco" does not satisfy these, the controller needs to hear the specific numbers back to catch an error before it becomes a runway incursion.
"Wilco" vs a full readback
"Wilco" ("will comply") is fine for instructions that don't carry one of the mandatory items above, for example acknowledging a general heading or altitude change in some contexts. It is not a substitute for reading back a runway number, a hold-short instruction, or a clearance to cross or use a runway.
Why runway crossings get special attention
A significant share of runway incursions trace back to a taxi or crossing clearance that was assumed rather than confirmed. Reading back "crossing runway [X]" explicitly gives the controller one last chance to catch a misunderstanding before an aircraft ends up somewhere it shouldn't be.
A generic trainer, not your local procedures
"Fairview Tower" and the callsign here are fictional, and phraseology can vary slightly by facility and situation. This tool teaches the general FAA readback discipline, not a specific airport's procedures, always follow your instructor, your examiner, and the controller actually on frequency.