I think it might be the first one: hiv infections. (hope this helps!)
Answer:
Magnetism
Explanation:
The refrigerator doors are made of <u>metal</u>, and we use <u>magnets</u> to hold papers and photos on their surfaces. Magnets attract metals such as iron, cobalt, nickel, etc. That is due to the physical property of matter called <u>magnetism</u>, which is related to the attraction force generated by a magnetic field.
B. Heart, because the heart circulates blood throughout your body.