The Term Cardiac Index Is BEST Defined by Which of the Following

The term cardiac index is BEST defined by which of the following statements?

A) The amount of blood pumped by the heart per unit of time
B) The amount of blood pumped by the heart per unit of time per square meter of body surface area
C) The amount of blood ejected with each contraction of the heart
D) The primary indicator of left ventricular performance reflecting pulmonary vascular resistance