Answer:
Correct answer is D. Roman Catholicism.
Step-by-step explanation:
Most of people in Canada are Christians, but D is correct because almost 40 percent of Canadians are Roman Catholic.
There are almost 25 percent of Protestants, while when it comes to Islam and Buddhism, they together are making around 5 percent of population.
That is why all other answers are wrong.
Reason why Catholicism is widespread in Canada is because Canada was in hands of France until 1763.