A．is essential to the efficient control of weeds
B．may lead us to be aware of the fact that the soil contains enormous quantities of seeds of numerous species
C．helps us to have a good idea of why seeds can lie dormant for years
D．provides us with the means to identify weeds at the seedling stage

A．a report of events, causes, and effects that is generally accepted by historians but which is, for the most part, unverifiable
B．an episodic account that lacks cohesion because records of the role of childhood, work, and leisure in the lives of historical figures are rare
C．an uncharted sea of seemingly unexplainable events that have meaning only when examined as discrete units
D．a record of the way in which a closed set of immutable psychological laws seems to have shaped events