Which sentence is the best conclusion for an essay that begins with this introductory sentence?

in some countries, the start of a new year is marked by the harvest of the yams.
a) the yam is important to the culture of many people.
b) people celebrate the start of a new year in many different ways.
c) some people celebrate the new year with an all-night celebration.
d) the yam harvest is an important part of and hope for the new year.