11.  B .

12.  B .

13.  B .

14.  The pleasure of Riding a Bicycle: \

15.  For example, an "A" will drift to a mediocre "B".

16.  So their grade drop from "A" to "B".

17.  For example, they waste a lot of time on virtual reality , such as playing the computer games and as a result , their "A" average in study drift to a mediocre "B".

18.  B: The Digital Michelangelo Project will use computer-controlled laser scanners to capture the sculptures in such detail that even tool marks will stand out, giving scholars an opportunity to examine Michelangelo's technique.

19.  B: A large scanner on a 20-foot truss that can measure distances down to a one-quarter millimeter.

20.  B: I expected our project to be historically significant, I never expected to start by correcting the history books.