The rare earth elements include a. the actinide series and the alkaline earth metals. b. the alkali metals and the transition metals. c. the lanthanide series and the actinide series. d. the lanthanide series and the alkali metals.

Complete the sentence. the lower the hydrogen ion concentration, the the ph. higher lower closer to 7 closer to 0

Light waves can move through , but they travel fastest when they move through a(n) .

Observation and experimentation have led many scientists to accept a theory about the origin of the universe. this theory is called the big bang theory. scientific evidence collected and observed by scientists around the world suggests that the universe is ever expanding from a hot and dense initial state. what makes this a scientific theory? (2 points)