51. --- Who is at the _____ of all this trouble.
--- I don’t know.
| A．base | B．bottom | C．reason | D．Cause |
＿＿＿page of the book is torn and＿＿＿cover looks very old．
| A．The； the | B．A； a | C．A； the | D．The； a |
In China,＿＿＿bicycle is＿＿＿popular means of transportation(交通)．
| A．the； a | B．a；不填 | C．the； the | D．a； the |
The more you listen to English, ＿＿＿you’ll feel in speaking English．
| A．the well | B．easily | C．the more easily | D．the easier |
．He had never envied the rich＿＿＿money．
| A．his | B．their | C．one’s | D．her |
．The young often＿＿＿the old in our town．
| A．helps | B．wants to help | C．help | D．helping |