A student is writing a research paper for her science class. The student wants to revise the draft to improve the development of ideas. Read the draft and complete the task that follows.
The steep walls of the Grand Canyon that plunge nearly a mile down into the earth reveal an amazing sequence of rock layers. The Grand Canyon is so long and deep that it allows geologists and visitors the opportunity to see a multitude of Earth's colorful layers. As you peer into the Grand Canyon, you can see many multi-colored stripes of land. The colorful layers are horizontally stacked on one another.
Each "stripe" of color represents a different rock layer. Nearly 40 rock layers have been identified to form the Grand Canyon's walls. Today when we look into the Grand Canyon, we are seeing Earth's layers revealed. It is a unique opportunity.
The report needs more supporting information. Choose the set of sentences that give the best information to be added after the underlined sentence to support the topic.
A.
Each rock layer settled into place millions of years apart for various reasons. Then, approximately five or six million years ago, the Colorado River started slowly carving out the canyon, exposing layer by layer.
B.
The landscape also hosts a multitude of plant and animal communities that you would not expect to see. Not only that, but many people have called the Grand Canyon home over the past thousands of years.
C.
In 1908 Theodore Roosevelt set aside the canyon as a National Monument. Then, in 1919 Congress officially designated the Grand Canyon as a national park.
D.
It is our responsibility as the current stewards of the Earth to pass on the gift of the Grand Canyon to future generations — pristine and perfectly preserved.