The author's primary purpose is to A. identify the influences informing a particular geological theory about the processes that have shaped Earth's surface B. identify differences between two views of the extraterrestrial impactors and argue that the phenomenon has influenced the development of plate tectonic theory C. argue that an explanation is based on a dubious evidence and propose an alternative explanation D. discuss an explanation and place that explanation under theoretical context E. suggest that apparent discrepancy poses a serious problem for a particular theory that many have believed