Thanks.
I meant A and C to be different, so based on Dr. Kamiya's explanation, C is the answer. Now please let me follow-up and expand.

The amount of pressing on the accelerator pedal (how much you press it)

A. Translates to how fast the engine revs to full rev (and increases torque?), so essentially "ICE's tend to increase the rpm even the initial feed of fuel and air is low."

B. Dictates at what rpm (and torque) the engine stays, and stays that way.
B.1 The carburetor/ECU regulates (up and down cycle) air/fuel intake so that the engine stays at that rpm (and torque).

C. Both actually, translates to how fast the engine revs (and increase torque) to the limit dictated, and the air/fuel intake is regulated (up and down cycle) so that the engine stays at that rpm (and torque).
C.1 Only ECUs can do this.
C.2 Only carburetors can do this.
C.3 Both ECUs and carburetors can do this.

Kasi when the clutch is engaged the tendency is to eventually stop the revolution, due to friction. Thats why sometimes you need to rev the engine first before engaging the clutch, so that the engine has a headstart against the incoming friction, tama ba?

Arrgh when pondering on this topic, it tends to be complicated, kasi may mga issues na lalabas, kaya ung modern vehicles ay dapat talaga ECU.