What is a possible origin of the German Girl Shrine on Pulau Ubin, according to Dr. William L. Gibson's research?

A. A British colonial monument to commemorate World War I
B. A Malay folk belief site, Datuk Keramat, that was later syncretized with Chinese nature worship
C. A Chinese ancestral worship site that was built on an ant hill
D. A German family's coffee plantation on the island during World War I
Answer: 