What would happen to the propagation of a neural impulse if the membrane potential (voltage) at the synaptic terminal did not cross the threshold to open voltage-gated calcium channels

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answer : Calcium channels would remain closed, causing the neural impulse to travel back to the cell body. ( B )

Explanation:

When the membrane potential at the synaptic terminal does not cross the given threshold to an open Voltage-gated calcium channels, the propagation of the neural impulse will travel back to the cell body and this is caused by the calcium channels to remaining  closed

a- all cells come from pre-existing cells