What is the chemical in groundwater called that causes cancer?

Which statements about the two fossil images are correct? 1. cave bears are ancestors of plateosaurus. 2. plateosaurus were present on earth before ostracoderms. 3. ostracoderms were the first to die. 4. plateosaurus died after the ostracoderms. 5. cave bears are the oldest fossils.

Scientists observed a rock stratum with fossil. if mollusks evolved before arthropod, where will their fossils be found.

What is the leading cause if water scarcity throughout much of the world