Which of the following explains why arteries have thicker walls than veins?
a. because arteries carry oxygenated blood
b. because veins carry deoxygenated blood
c. because arteries carry high pressure blood from the heart
d. because veins also carry blood from the lungs into the heart

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?

(select all the correct choose each statement that is scientific. - the opinions of randomly selected participants in a survey prove the idea that global temperatures are not increasing on earth. - the universe's average temperature and rate of expansion support the idea that it began as one super-dense and hot mass 13.8 billion years ago. - ocean tides are caused by the uneven gravitational pulls of the moon and sun on different parts of earth. - human life is more valuable than other forms of life on earth because humans are more intelligent than other organisms.

Environmental science are unconsidered with methods to preserve natural resourcesa.trueb.false