D) 4 and 5
 

                             1. The preferential tariffs offered by Britain to its colonies.
                             2. The removal of taxes on exports of Canadian timber to the United States.
                             3. Napoleon's blockade of European ports against British ships.
     Not Correct !  4. The lack of timber reserves in Europe.
     Not Correct !  5. Britain's adoption of a policy of free trade with its colonies.