Which sentence uses correct parallel structure? a. throughout history, india has been a hub of civilization, it has been referenced frequently by far-removed cultures, and it's an academic powerhouse. b. our three main objectives are removing lead from the water supply, replacing the broken pipes, and getting the water flowing again as fast as possible. c. colorado is a state with a great deal of natural beauty, including mountain peaks, fast-moving rivers, and it also boasts some world-famous ski slopes. d. the curricula of most school districts in the united states tends to be dominated by english, math, history, and science is also extremely important as well.