How do parasympathetic neural signals affect the working of the heart?

What happens to the heart rate if the parasympathetic nerve of a rabbit is cut?

Cardiac activities of the heart are regulated by:
$A.$ Nodal tissue
$B.$ $A$ special neural centre in the medulla oblongata
$C.$ Adrenal medullary hormones
$D.$ Adrenal cortical hormones
Choose the correct answer from the options given below:

Stimulation of the vagus nerve will make the heart beat

Read the following statements:
$I$ - Increased heart rate.
$II$ - Increased ventricular contraction force.
$III$ - Decreased cardiac efficiency.
$IV$ - Increased cardiac efficiency.
$V$ - Decreased heart rate.
$VI$ - Decreased conduction speed of action potential.
Categorize the given statements into Sympathetic and Parasympathetic nervous systems.
Sympathetic Nervous System $\quad$ Parasympathetic Nervous System

Assertion $(A) :-$ Parasympathetic neural signals decrease the cardiac output.
Reason $(R) :-$ Parasympathetic neural signals decrease the rate of heartbeat and the speed of conduction of action potentials.