A Tiny, Tawny Colored Butterfly Called the Carson Wandering Skipper

A tiny, tawny colored butterfly called the Carson Wandering Skipper was always known for its small and very localized populations. Typically, it was found along the western Nevada and eastern California high desert areas. It was always located close to hot springs and other wet areas that supported salt grass, the host plant it depended on.Recently, the populations went into a steep decline, and a last hold-out area was threatened by imminent construction of a freeway bypass. Biologists became alarmed and began an intensive search for populations in locations other than the spot designated for the freeway bypass. They began their search by identifying all known locations of hot springs, in hopes of finding small populations of the Carson Wandering Skipper close by.
-The biologists' observations that the Carson Wandering Skipper populations had declined is an example of

A) data analysis
B) identifying a problem
C) performing an experiment
D) proposing a hypothesis
E) making testable predictions