Which event helped get the voting age lowered to 18?

Which number is main idea? i need answer quick. (1) people may think that love and romantic feelings are enough of a basis for choosing a spouse. (2) the chances of a marriage surviving, however, would improve if prospective marriage partners considered a few unromantic questions before deciding on matrimony. (3) for example, do the two individuals involved share a common socioeconomic background? (4) the more similar they are in their social, economic, religious, and cultural backgrounds, the more similar their expectations about married life will be. (5) in addition, what are their goals? (6) it’s a big advantage to the marriage if they know and share one another’s goals concerning career, lifestyle, and family. (7) finally, and maybe most important, how does the prospective spouse treat others in his or her life? (8) during the courtship, the boyfriend or girlfriend may get special consideration, but in the long run, spouses will probably treat each other about the same way they treat their own family members.

Assessment includes a. interviews, recorded conversations, videos, frequency counts, and time samples. b. formal standardized tests and developmental screening tools. c. various types of documented observations, documentation of child work, checklists, rating scales, and standardized tests. d. anecdotal notes, narratives or daily records, daily health checks, and teacher observation checklists.

Mount saint helen the great lakes and death valley are physical features of the earth which scientific term describes these features