What was the main idea of the science article by tyrone nielson

Im going to assume that the article you re referring to is ' How pluto stopped being a planet ' by Tyrone Nielson.

The main idea of the article is that a group of astronomers decided not to recognize pluto as part of our solar system by calling it a dwarf planet. But they do not call it that because of its size, but in order to be called a planet it has to follow three conditions, of which it does not fulfill the thrid one, which is that a planet must attract smaller objects to itself or pull them to its orbit or throw them into space but pluto moves with a field of rock and ice that can not be rid of. That s why the name of dwarf planet.

"choosing is refusing" means individuals face an opportunity cost with each decision they make. economists state that every decision involves trade-offs. opportunity cost is the least desirable alternative given up as a result of a decision.

the answer to your question is,

d. when a child was born.

-mabel < 3