3. What occurs most frequently at a transform boundary? A) volcanos
B) rift valley
C) mountains
D) earthquakes

not sure if this what   you'r looking for would be percent composition

the question isn't complete here so i can't right an answer '_'

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.