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Identify the relative clauses in the following sentences and, if possible, change them into reduced relative clauses.
Immigration, which was under strict regulations in the 1960s, placed certain obstacles in the way of people from some countries.
Immigration, which was under strict regulations in the 1960s, placed certain obstacles in the way of people from some countries.
Immigration, strictly regulated in the 1960s, placed obstacles in the way of people from some countries.