<p>Air pollution cause by industrial fume [has been studied] for years, [but] only recently [has] the harmful effects of noise pollution [become] known. [no error]
answer: C. has </p>
<p>[Quick to] [take advantage] of melanie johnson's [preoccupation in] the history of the johnson family, the genealogist proposed investigating [that] history- for a large fee.
answer C preoccupation in </p>
<p>[Contrasting with] [most other] fifteenth-century rulers, Portuguese kings [could count on] the support of the aristocracy [in any] overseas adventure.
answer: A. contrasting with</p>
<p>can anyone please explain to me the errors in the sentences? thanks</p>