because sentece b is the explanation of sentence c which is why the guirrella losses their ability to disengage etc.
hope this helps
stress relief can be achieved with chemicals in freshly-cut grass, according to scientists.
more than 20 percent of the world oxygen is produced in the amazon rainforest.
plants dislike human noise.
the rise of English is a remarkable success story. When Julius Caesar landed in Britain nearly 2,000 years ago, English did not exist. Five hundred years later, Englisc, incomprehensible to modern ears, was probably spoken by about as few people as currently speak Cherokee--and with about as little influence. Nearly a thousand years later, at the end of the 16th Century, when William Shakespeare was in his prime, English was the native speech of between 5 and 7 million Englishmen, and it was, in the words of a contemporary, ''of small reatch, it stretcheth no further than this iland of ours, naie not there over all.''
Four hundred years later the contrast is extraordinary. Between 1600 and the present, in armies, navies, companies and expeditions, the speakers of English--including Scottish, Irish, Welsh, American and many more--traveled into every corner of the globe, carrying their language and culture. Today English is used by at least 700 million people, and barely half of those speak it as a mother tongue. Some estimates have put that figure closer to 1 billion. English at the end of the 20th Century is more widely spoken and written than any other language ever has been. It has become the language of the planet, the first truly global language.