Since scientists began collecting data on earthquakes in the 1960s, what have they realized about tectonic plate boundaries? ? a) they are concentrated at plate boundariesb) they happen at set timesc) they occur at the same placed) they mostly occur at divergent plate boundaries

The appropriate answer is a. Scientists have realized that earthquakes are concentrated at plate boundaries. The plate boundaries represent the regions where two or more tectonic plates interact with each other. There are three types of plate boundaries, Convergent, Divergent and Transform. Plates move apart at divergent and come together at convergent. They slide past each other at transform boundaries. 

26.4 is about the right time