Is a method of ratification in which the voters, rather than the legislature, vote on an issue.
a. an amendment
c. an initiative
b. a referendum
d. a constitutional convention

b. A referendum

Explanation:

The answer is referendum because it is a method in which all the people in a country that are qualified to vote are invited to do it on a particular subject and the result of this is the adoption or not of a new law.

The other options are not correct because an amendment is a change made to a law, an initiative is a petition to force the government to enact a law and a constitutional convention is a meeting to write a new constitution or to make changes to the one in place.

c. taught scientists many new things about the earth, but not other planets.

explanation: