Based on the provided statements, Species C would most likely be classified as an invasive species in the United States.
Species C is described as a plant from Japan that grows aggressively (up to a foot per day), smothers low-growing plants, and kills trees. Additionally, it has no natural predators, which allows it to proliferate uncontrollably and disrupt local ecosystems. These characteristics align with the definition of an invasive species, which is a non-native species that causes harm to the environment, economy, or human health.
In contrast, the other species mentioned either do not exhibit such aggressive growth or negative ecological impacts, making them less likely to be classified as invasive.