Which of the following statements is correct about mountain pine beetles? 

A)  They are medium-size brown bark beetles that are devastating pine forests in the Appalachian Mountains of Quebec and Labrador. 
B)  They are small dark-coloured native bark beetles that are currently infesting, damaging and destroying pine trees in western Canada. 
C)  They are red-and-white pine beetles, originally native to China, that are attacking high-altitude pines in southern British Columbia. 
D)  They are an invasive species of beetle, originally from cool high-altitude pine forests of the U.S., that have crossed the border into Canada and started infesting our cool-temperature northern pine forests.