For one-family dwellings supplied by a single-phase, 120/240-volt system, and having a 200-ampere rated inverse time circuit breaker for the main disconnecting means, what minimum size THWN aluminum conductors are permitted for use as ungrounded service-entrance conductors? Given: No adjustment or correction factors are required.

Most states require an electrician to pass an exam to receive a journeyman or master electrician license.  State exams cover these topics:  Electrical Theory, Trade Knowledge, Grounding and Bonding, Wiring Methods and Installation, Overcurrent Protection, Load Calculations, etc.