The number of specialists has enormously increased mainly because of ______.

A．academic mobility may enhance scientific research
B．academic mobility may promote interpersonal relations
C．scientific researchers may be subject to misunderstanding
D．scientific researchers work in collaboration worldwide

A．IParadigms have a system of charges that varies from users to users.
B．There are a variety of plagiarism-detection tools available today.
C．We can depend on the detection tools for actual plagiarism.
D．Plagiarism-detection service is relatively cheap.