Refer to the Graph Showing Data from a Set of Hydroponic

Refer to the graph showing data from a set of hydroponic experiments examining the dependence of germination on nickel levels.A number of plants are grown at different nickel concentrations for three generations.Some seeds from third generation plants are analyzed for nickel content, and some are germinated in solution lacking nickel.Many of the seeds germinate. Which conclusion is valid?

A) Since more seeds germinate in the low nickel conditions, there must be too much nickel present.
B) The lack of nickel in the germination solution compensates for too much nickel in the seeds.
C) High levels of nickel are toxic to the plant.
D) When plants are grown with sufficient nickel, their seeds contain enough nickel to allow germination.
E) There must be small amounts of nickel present in the germination solution to allow the seeds to germinate.