A state passes a law requiring mandatory seatbelt use and claims it has reduced traffic fatalities. While the seatbelt law was changed, speed limits were also reduced from 70 MPH to 55 MPH by the federal government. Traffic fatalities decreased during the first year of the seatbelt law. The change in the speed limits represents what kind of threat to internal validity?

Group of answer choices

Maturation effect

Instrumentation effect

Testing effect

History effect