Which one of the following geologic time periods is associated with the first appearance of the marsupials?

Marsupials belong to the clade Metatheria, which diverged from placental mammals (Eutheria) during the Mesozoic Era. While the divergence is presumed to have occurred early in the Cretaceous, the fossil record provides specific evidence for their emergence. The first unequivocal metatherian fossil, such as Sinodelphys, dates back to the Early Cretaceous of Asia. This period, which began approximately 145 million years ago, saw the initial radiation of these lineages. Although marsupials became taxonomically and morphologically diverse in the Late Cretaceous of North America [4], their earliest appearance is documented in the Lower (Early) Cretaceous. By the earliest Late Cretaceous (Cenomanian), they were already established in the New World, but the ancestral forms first appeared in the preceding Early Cretaceous epoch [1].

Sources

1. [1] https://www.nature.com/articles/325520a0
2. [4] https://discovery.ucl.ac.uk/10043033/7/Upchurch%20Vor%20_div_class__title__Deep_time_diversity_of_metatherian_mammals__implications_for_evolutionary_history_and_fossil-record_quality__div_.pdf