Question

study background:
in the 1970s, the epa started phasing out the use of lead in gasoline. by the early 1990s, lead was completely removed from gasoline. over time, lead samples in gasoline were collected. also, select people were tested for the presence of lead in their blood. the results from both samples are shown in the following graph.
what can be concluded from this graph?
removing lead from gasoline in the 1970s was an ineffective policy regulation.
there is a correlation between blood lead levels and the use of lead in fuel.
people should strongly minimize their exposure to lead while filling their gas tanks.
running errands without consolidating trips does not affect lead exposure.

Explanation:

Since lead was removed from gasoline over time (as per the background) and blood - lead levels would be expected to change in relation to gasoline lead levels (a common environmental health concept), a correlation between blood lead levels and fuel lead use is a logical conclusion. Removing lead from gasoline was effective (so the first option is wrong). There is no information in the given text about gas - tank filling exposure (so the third option is wrong) and no mention of trip - consolidation (so the fourth option is wrong).

Answer:

There is a correlation between blood lead levels and the use of lead in fuel.