Final answer:
Opening many Cl^- gated channels would increase the magnitude of the resting membrane potential.
Step-by-step explanation:
Resting Membrane Potential (RMP) and Cl^- gated channels
The resting membrane potential (RMP) is the electric potential difference across a cell membrane when the cell is at rest. It is typically around -70 millivolts (mV) and is maintained by the movement of ions across the cell membrane. If many Cl^- gated channels are suddenly opened, it would lead to an influx of Cl^- ions into the cell, which is negatively charged. This influx of negative ions would make the inside of the cell more negative, thereby increasing the magnitude of the resting membrane potential (making it more negative).