The pacemaker in frog heart is:
A. SA node
B. AV node
C. Conus arteriosus
D. Heart muscles

Hint: The heart of the frog has three chambers, one ventricle, and two atria. Blood leaves the heart from the ventricle through a solitary truncus arteriosus which is short and before long branches into two aortic curves which circle left and right and dorsal to the heart to rejoin as a solitary aorta in the mid-dorsal district of the body depression. Each aortic curve has a branch prompting the lungs and skin where oxygenation happens.

Complete answer:
1. In Amphibians, for example, the frog, the pacemaker is the sinus venosus, an augmented area between the vena cava and the correct chamber. The atria are conductive, and the activity potential spreads promptly over these two chambers. So, option A is correct.
2. The atrioventricular (AV) hub is a little structure in the heart, situated in the Koch triangle, near the coronary sinus on the interatrial septum. In a right-predominant heart, the atrioventricular hub is provided by the correct coronary corridor. So, option B is incorrect.
3. The conus arteriosus is the thin cylinder extending anteriorly between the atria from the correct side of the ventricle. So, option C is incorrect.
4. Cardiovascular muscle tissue is just found in the heart. Like skeletal muscle, the heart muscle is striated. So, option C is incorrect.

So, the correct answer is “Option A SA node”.

Note: A specific solid tissue called SA hub is situated in the upper right corner of the right auricle and aides in starting the cadenced withdrawals of the heart. The cells that make these musical motivations, establishing the tone for blood siphoning, are called pacemaker cells, and they legitimately control the heart rate. They make up the cardiovascular pacemaker, that is, the normal pacemaker of the heart. Electrical impulses generated from the heart muscle cause a frog's heart to beat (contract). This electrical signal is generated in the sinoatrial (SA) node.