Choose the word that best completes the sentence.
in order to ensure the proper balance of sub-topics in the research paper, it is important to make sure that the outline is
a. grammatical
b. parallel
c. subordinate
d. complex

[1] when the twins grew up, they continued to fight. [2] one day they decided to hold a contest to determine who was stronger. [3] though they tried to defeat each other in many different ways, neither one could win. [4] on the last day, they fought with weapons. [5] using a deer antler, the right-handed twin overpowered his brother, and he threw him off the edge of the earth. [6] today, the right-handed twin lives in the sky-world, and the left-handed twin lives in the dark underworld. [7] they rule the earthly world of men together.