The following verbs are generally used with these prepositions:

d The president who enjoyed playing jazz was elected for a second term. e A hurricane is a tropical storm that can do enormous damage.

5. In defining clauses both that and which can be used with things.

Toyota is a Japanese company thatwhich makes cars. But for clauses that provide additional detail only which can be used: Volkswagen, which is a German company, is a major car producer. In defining clauses where the relative pronoun is the object its use is optional: She applied to the university thatwhich her tutor had recommended. The course thatwhich I wanted to take was not offered this semester. The tutor who she wanted to meet was away for two months. When the relative pronoun is the subject it must be included: The scientists who discovered DNA worked in Cambridge. Decide if the relative pronouns in the following are necessary. If not, cross them out. a It was not known who was responsible for the explosion. b The man who I read about was born in Scotland. c The book that the professor wrote was remarkably short. d Squirrels are mammals that live mainly in trees. e The article that she referred to was published last year.

6. Insert a suitable relative pronoun in the text below. Write X if the pronoun is optional.

King Camp Gillette, a . . . . . . . . . . . . . . . . invention of the disposable razor blade made his name world-famous, was an American b . . . . . . . . . . . . . . . . had spent 40 years looking for a saleable invention. The idea c . . . . . . . . . . . . . . . . changed his fortunes occurred in 1895, but he met considerable difficulties producing a thin, sharp blade d . . . . . . . . . . . . . . . . could be made cheaply. He sold shares in the company to pay for the development work e. . . . . . . . . . . . . . . . his partner, William Dickerson, was doing. In 1903, f . . . . . . . . . . . . . . . . was their first year of business, they produced only 51 razors. But due to intensive advertising, g . . . . . . . . . . . . . . . . potential Gillette quickly recognised, they rapidly increased sales to 250,000 two years later. The modern razor, h . . . . . . . . . . . . . . . . is usually double- bladed, is directly related to the idea i . . . . . . . . . . . . . . . . Gillette had over a hundred years ago.