On a piece of paper, use a protractor to construct △abc with m∠a=30° , m∠b=60° , and m∠c=90°. Which statements about the triangles are true? select each correct answer.

Which of the following always exist between two objects having mass ● elastic force ● contact force ●gravitational force ●magnetic force

Earth's atmosphere is unique among the planets and is able to support life because it contains a large amount of a) oxygen b) helium c) methane d) carbon dioxide

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.