Which of the following statement is incorrect?

Our heart has four chambers, two relatively larger upper chambers called atria and two smaller lower chambers called ventricles.

The correct answer is Option (3) - Our heart has four chambers, two relatively larger upper chambers called atria and two smaller lower chambers called ventricles.

Human circulatory system, also called the blood vascular system consists  of a muscular chambered heart, a network of closed branching blood vessels and blood, the fluid which is circulated.
Heart, the mesodermally derived organ, is situated in the thoracic cavity, in between the two lungs, slightly tilted to the left. It has the size of a clenched fist. It is protected by a double walled membranous bag, pericardium, enclosing the pericardial fluid. Our heart has four chambers, two relatively small upper chambers called atria and two larger lower chambers called ventricles. A thin, muscular wall called the inter- atrial septum separates the right and the left atria, whereas a thick-walled, the inter-ventricular septum, separates the left and the right ventricles .

The atrium and the ventricle of the same side are also separated by a thick fibrous tissue called the atrio-ventricular septum. However, each of these septa are provided with an opening through which the two chambers of the same side are connected.