Explain why the pulmonary circuit must operate at a lower pressure than the systemic system

P. Circuit is the lungs takes blood from the right side of the heart goes out the artery goes to lungs goes out veins dumps to left side to oxygenate the blood.
Left side s. Circuit delivers oxygenated blood to body goes down the left centric goes to aorta and goes to head and body from there.

The los angeles must have 500 to 900words

How how am i supposed to know