Điền từ thích hợp

           those                      countries                  system                        rule                     two   

                                                        The right side is the wrong side!

          Do you know that there are many (1) __ countries  ___ in the world where the traffic (2)__rule__ is to keep to the left? Some of (3) ____ those _ are the United Kingdom, Australia, Thailand, Malaysia, etc. There are different reasons for this. One is that some countries used the same (4) ___ system _______ as the UK. Another is that many people are right-handed!