In Which of the Following Situations Would Speciation Be Most

Multiple Choice

In which of the following situations would speciation be most likely to occur?

A) A population of juniper shrubs is split in two by a canyon. Every year, strong winds carry a small amount of the shrubs' pollen across the canyon.
B) A Japanese mollusk species whose larvae are often carried from port to port in ship bilge (waste) water now flourishes in San Francisco Bay, a busy commercial port.
C) Bighorn sheep occupy mountains from Canada to Death Valley in Southern California, interbreeding all the way. The populations at the two ends of the range live in very different environments.
D) Seven monkeys escape from an enclosure. To everyone's surprise, they establish a small but viable population, coexisting successfully with humans in a partly suburban environment very different from their native African habitat.