Depends on how deep you're willing to go to really,
You need one of a few arrangements of flip flop circuits to keep 1-bit state.
Going deeper, you need either NAND, or NOR gates(or a bunch of other ones) and connectors.
Even deeper, you'll require diodes or transistors to build the logic gates.
Beyond that is particle physics.
Answer:
the bottom third
Explanation:
Check out the exampe below.
swim() would be an example of a method.
Answer:
Open loop control systems.
Closed loop control systems.
Explanation: