Final answer:
The new trait that appeared with the arrival of angiosperms is the presence of flowers, which allow for specialized pollination and efficient seed dispersal.
Step-by-step explanation:
The new trait in land plants that appeared with the arrival of the angiosperms is c. the presence of flowers. Angiosperms, also known as flowering plants, are characterized by their ability to produce flowers that enclose their seeds within a carpel. While the presence of vascular tissues and seeds was already exhibited by earlier groups of plants like gymnosperms and seedless vascular plants, the development of flowers was a significant evolutionary advancement that distinguished angiosperms. This adaptation allowed for more efficient and specialized pollination mechanisms, greatly enhancing the angiosperms' ability to spread and dominate in various ecosystems.