Martha was the only girl in her class to be accepted into the prestigious university.
Italics are used in the sentence above because the italicized words are:

Question

Quizplus · Accepted Answer

The word "only" is italicized because Mary was the only girl in her class to be accepted, which is a cause for emphasis. 
The scientific name of an organism is incorrect. The word "only" is italicized because Mary was the only girl in her class to be accepted, which is a cause for emphasis. Nothing in the sentence involves a scientific name of an organism. 
Words that the reader may not know is incorrect. The word "only" is italicized because Mary was the only girl in her class to be accepted, which is a cause for emphasis. The italicized word is not a word that the reader would not know. 
A proper title of something is incorrect. The word "only" is italicized because Mary was the only girl in her class to be accepted, which is a cause for emphasis. Proper titles are not included in this sentence.

Martha Was the Only Girl in Her Class to Be