The correct answer is - d. timber and oil.
Canada is very large country that has very big amounts of certain very valuable natural resources. The two most important natural resources of the second biggest country in the world are the oil reserves, and the timber.
Canada is slowly but surly becoming a major player on the global oil trade market. It is estimated that the country has the third largest oil reserves in the whole world, and most of those reserves are still not exploited, which gives the country a huge economic boost for the years to come.
The timber is trademark Canadian resource, and the country has it in abundance. Canada is one of the top countries in the world by forest occupied area, and it is widely using the timber for lots of products, and for exporting in other countries that lack it.