Guessing the words you are comparing are "plain" and "plains" the correct answer is C. Homophone; the two words are pronounced the same but have different meanings and sometimes different spellings. Because <em>plain</em> and <em>plains</em> are words that sound alike; but they have different meanings as in "<em>plain</em> cream cheese" the word plain means to be pure while the word <em>plains</em> in the part "crossing the plains in Kansas" is referring to the extensive area of Kansas country; lastly they have slightly different spellings as plain and plain<em>s</em>.
Option A. Homograph is wrong because the correct definition is two words are written the same, not pronounced the same.
Option B. Homophone is wrong because the correct definition is two words are pronounced the same, not written the same.
Option D. Homograph is wrong because in this case they are written the same as the <em>bear </em>(the verb to carry) and the <em>bear </em>(the animal). But for <em>plain</em> and <em>plains</em> they are not identical as one has a <em>S.</em>
Sibilings is correct. Siblin is wrong.
Answer: The Rosetta Stone was discovered in the nineteenth century in ancient Egypt by expert scholars.
This sentence is the best one as a thesis if the only source of information is this passage. The other sentences add information that has not been mentioned before (the stone's role in deciphering hieroglyphs, the material it is made out of or its impact on tourism). This sentence does not add information and at the same time summarizes the most important elements of the passage.
