Five million, five hundred and fifteen thousand, one hundred and fifty-one is ______.

1. A.
   5,515,151
2. B.
   5,151,151
3. C.
   5,151,515
4. D.
   5,551,155

Five million, five hundred and fifteen thousand, one hundred and fifty-one is ______.

Electronic books have changed the way many people read for   15 . Now online textbooks are changing the way some students learn and some teachers teach.

More than   16  students go to the public schools in Fairfax County, Virginia, outside Washington. Last year, the school system used digital books in fifteen schools. This school year, middle schools and high schools changed   17  printed to electronic textbooks in their social studies classes.

“I mean, it’s just   18  a regular textbook, except it’s got it all online.” says Luke Rosa, a history teacher at Falls Church High School.

Peter Noonan, an assistant superintendent(主管) of schools says, “The world’s changing   19 . And the online textbooks can change right along with the events that   20 .”

“Digital books also cost   21  than printed textbooks,” he says, “Usually it’s between fifty and seventy dollars   22  a textbook for each student, which adds up to about eight million dollars for all of our students in Fairfax County. In fact, we have bought all of the online textbooks for our students for just under six million dollars.”

Social studies teacher Michael Bambara says the e-book he uses in his government class is better than a(an)   23  textbook. It has materials for students   24  different levels of reading skills…