What term(s)/value(s) are not relative but absolute?

d. the current in the base that turns the transistors on.

While using Transistor as switch, in the switch off state the current in base is 0. To switch on the transistor, a current at base is required that allows the flow of current through the transistor like a small amount of water is poured to prime the pump. The current won't flow through the transistor unless the biasing of base allows the current.