The correct option is
B Three chambered
The blood vascular system consists of lymph, lymph channels, and lymph nodes. The heart is a muscular structure situated in the upper part of the body cavity. It has three chambers, two atria, and one ventricle and is covered by a membrane called pericardium. The ventricle opens into a sac-like conus arteriosus on the ventral side of the heart.
So the heart of the frog has three chambers.So, the correct answer is 'Three chambered'.