Which body system has a main focus on the heart, blood and veins?

a. nervous

b. circulatory

c. urinary

d. skeletal

Nervous system deals with the brain, nerves, and electrical signals

circulatory system deals with the heart, blood, and veins

urinary system is the system in which we rid the body of liquid waste / urine/pee

skeletal system is the skeleton

these are all very general definitions that you could easily look up