A) 1 and 3          
 

Correct !          1. The preferential tariffs offered by Britain to its colonies.
                         2. The removal of taxes on exports of Canadian timber to the United States.
 Correct !         3. Napoleon's blockade of European ports against British ships.
                         4. The lack of timber reserves in Europe.
                         5. Britain's adoption of a policy of free trade with its colonies.