Four Rules for One Cell

A model neuron, built on the biological idea, receives three signals: $A$, $B$ and $C$. Each signal is either active or silent, and each has its own strength, which is a positive number.

The cell body adds up the strengths of the signals that are active. If that total is at least the neuron's threshold (also a positive number), the neuron fires. Otherwise it stays quiet. It is all-or-nothing: there is no half-firing.

You choose the three strengths and the threshold. Each option below is a firing rule you might want the neuron to follow. In them, "$A$ is active on its own" means $A$ is active while $B$ and $C$ are both silent.

Which rule can no choice of strengths and threshold produce?