Chordae tendinae

Which artery carries deoxygenated blood instead of oxygenated blood?

Right atrium: Coronary sinus:: Left atrium: . . . . . . .

During human fetal development, the pulmonary artery is connected to the aorta by a narrow duct called the ductus arteriosus. What is this structure called after it closes and becomes a fibrous remnant in an adult?

In humans,blood passes from the post caval vein into the diastolic right atrium of the heart because of:

Assertion : Muscle fibres of $SA$ node possess the lowest rhythmicity among all cardiac muscles.
Reason : Due to this fact,it can initiate excitatory waves at the highest rate.