Which of the Following Would Be Most Vulnerable to Extinction

Which of the following would be most vulnerable to extinction?

A) a healthy plant, such as a pine tree, that completely dominates its native environment
B) a mold that attacks wheat in the field
C) a moth, brought to the United States for silk production, escaping into the wild and becoming established
D) a migratory flock of warblers stopping along its winter route to feed on local resources that are now gone and replaced by a suburb
E) an orchid endemic to a forest where logging is occurring