Relative pronouns after prepositions: is it okay to use them in speech?
Consider the following usages of relative pronouns: 1. The lecturer introduces a study *in which* participants were asked to choose one attractive picture. 1. At the university I met famous professors, *many of whom* were fluent English speakers. One of my grammar textbooks says that these usages are bookish. The question is whether I sound strange if I use relative pronouns in these ways in speech (I have TOEFL speaking section in mind). This may not be a relative pronoun technically, but people sometimes write *I have no pen with which to write letters* instead of *I have no pen to write letters with*. Is the former expression too formal to be used in speech?