Which is the best example of commensalism? a. honey bees feed on the pollen of cornflowers and the flowers reproduce. b. barnacles ride on a gray whale’s back to obtain food, and the whale is not harmed. c. squirrels and chipmunks eat the same nuts in a forest where food is scarce. d. prairie dogs often collect and eat food in groups so they are better protected from enemies.

The molecular formula for caffeine is cshion402. which of the following elements is not found in caffeine?

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

Balance the following reaction. as2s3 + 9o2 → 2as2o3 + so2