Examination positions, together with most business letters and government reports, are the main situations formal language is used.
A. in which
B. on which
C. of which
D. for which
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A. in which
B. on which
C. of which
D. for which
解析：
考查定语从句在语境中的具体运用。先行词为situation应用介词in：in the situation。