question: What American director of M1 , M2 , and M3 was M4 's director
query: SELECT DISTINCT ?x0 WHERE {
  ?x0 ns:film.director.film M1 .
  ?x0 ns:film.director.film M2 .
  ?x0 ns:film.director.film M3 .
  ?x0 ns:film.director.film M4 .
  ?x0 ns:people.person.nationality ns:m.09c7w0
  }