17．A．before                 B．when                   C．since                   D．until

16．A．invent                 B．inventing             C．invented              D．to invent

15．A．This                    B．It                        C．I                         D．That

（B）

The bicycle is one of the simplest yet most useful inventions in the world．What is most surprising is that it was not  16  earlier, although the great inventor Leonardo da Vinci had drawn pictures for bicycles and also for flying machines and some other things．Those things were not produced  17  long after he died．

A person riding a bicycle uses  18  energy（能源）to make the bicycle move, and there is no pollution（污染）at all when you are riding．Even so, in developed  19  , most people don’t travel to work by bicycle．It is not because the bicycles are expensive or people feel  20  if they tide to work．It’s because  21  cars on the roads becomes larger．It certainly becomes  22  to ride a bicycle．As a result, more people put their bicycles away and go to work  23  their cars and, in this way, the situation（情形）is made more serious． 24  the best way to make tiding safer and more popular is to create paths（开设通道）only for bicycles, and to make  25  so difficult and expensive for drivers to take their cars into the city that they will go back to using their bicycles．

14．A．question              B．ask                      C．understand           D．study

13．A．grass                   B．animals                C．people                 D．trees

12．A．lives                    B．living                  C．live                       D．life

11．A．space                   B．size                     C．colour                 D．age

10．A．after                    B．at                     C．for                        D．like

9．A．good                     B．long                    C．bad                        D．colourful

8．A．legs                      B．teeth                    C．nose                    D．feet