Answer:
Paleontologists don't know for certain, but perhaps a
large body size protected them from most predators,
helped to regulate internal body temperature, or let
them reach new sources of food (some probably browsed
treetops, as giraffes do today). No modern animals
except whales are even close in size to the largest
dinosaurs; therefore, paleontologists think that the
dinosaurs' world was much different from the world
today and that climate and food supplies must have
been favorable for reaching great size.
