Question

lowered extracellular k+ levels will lower the heart rate because
multiple choice
more na+ channels open.
it blocks ca2+ channels.
action potential amplitude declines.
ectopic action potentials occur.
the resting membrane potential is hyperpolarized.

Explanation:

When extracellular K⁺ levels are lowered, the electrochemical gradient for K⁺ increases. More K⁺ diffuses out of the cell, making the resting membrane potential more negative (hyperpolarized). A hyperpolarized resting - membrane potential means that more stimulus is required to reach the threshold for an action potential, thus slowing down the heart rate.

Answer:

the resting membrane potential is hyperpolarized.