Which statement best describes arteries? a) all carry oxygenated blood to the heart. b) all carry blood away from the heart. c) all contain valves to prevent the backflow of blood. d) only large arteries are lined with endothelium.

lichens that colonize bare rock secrete acids that break down the rock and start the soil-production process. so they expose rocks

the correct answer is;

because they only contain one pair of trunks.

the reason why two elephants cannot swim together is that they have one pair of trunks and they can not share it, that's why they can not swim together.

besides these elephants are giant animals. they belong to the family of mammals mainly found in sub-saharan africa, south asia, and southeast asia.