Which of the following reference is the citation of an online journal article?

A、Langner, M., & Imbach, R. (2000). The University of Freiburg: A model for a bilingual university. Higher Education in Europe, 25(4), 461–468. https://doi.org/10.1080/03797720120037796;

B、Hofman,
C、
A、, & Rick, T.
C、 (2018). Ancient biological invasions and island ecosystems: Tracking translocations of wild plants and animals. Journal of Archaeological Research, 26(1), 65–115.;

C、Pollack, M.
E、 (2005). Intelligent technology for an aging population: The use of AI to assist elders with cognitive impairment. AI Magazine, 26(2). https://www.aaai.org/;

D、Greenslade, R. (2018, July 29). Opinion is valued more than fact in this digital era. The Guardian. https://www.theguardian.com/