11.
（a） the author also drew illustrations for her book.
（b） the author has included some of her life in the book.
（c） the author is experienced at writing fiction.
（d） the identity of the author is unknown.
12.
（a） this was the second concert we attended.来源：www.examda.com
（b） we had a good time even though it was cold.
（c） the loyal fans enjoyed the chilly weather.
（d） the next concert will be outdoors despite the forecast.
13.
（a） i was assigned to the wrong class.
（b） i had mixed feelings about the class.
（c） i was confused about my class schedule.
（d） i had to stand up during class.
14.
（a） the cafeteria will not be serving meals today.
（b） the cafeteria will be open for just one meal.
（c） the cafeteria always prepares delicious holiday food.
（d） the cafeteria will be closed for breakfast only.
15.
（a） he shouldn't climb stairs.
（b） he climbed dozens of steps.
（c） where do more steps go?
（d） are these the stairs be climbed?
16.
（a） a piece of paper marked the page.
（b） there were marks in the book.
（c） the book was misplaced.
（d） the paper is underneath the book.
17.
（a） there's really no need for a new school.
（b） there's a lot more to do on the new school.
（c） the new school is nowhere near here.
（d） the new school is almost completed.
18.
（a） we had hardly eaten anything when we heard the doorbell ring.
（b） the doorbell rang as we were about to go out to dinner.
（c） we listened for the doorbell. but our guests never came.
（d） just before dessert was served, the doorbell rang.
19.
（a） i read the papers yesterday afternoon.
（b） the papers were already finished when i arrived.
（c） the documents can be signed later today.
（d） i expect the sign to be ready this afternoon.
20.
（a） she discovered a problem with the vaccine.
（b） she was critical of the new development.
（c） the vaccine couldn't have been created without her.
（d） she was criticized for developing the risky vaccine.
