Answer: A. Cavalry
Explanation: The "blitzkrieg" is a military tactic that was created by the Germans during World War 2. Speed is a requirement as a blitzkrieg is meant to overpower the enemy before it has time to prepare for battle or receive aid from allies. Tanks and planes are also key components as they are powerful and maneuverable, which is also needed for a blitzkrieg to be successful. Cavalry is not, and never was, needed for a blitzkrieg.