question: What employer of M4 's employee was acquired by M0 , acquired by M1 , acquired by M2 , and acquired by M3
query: SELECT DISTINCT ?x0 WHERE {
  ?x0 ns:business.employer.employees/ns:business.employment_tenure.person ?x1 .
  ?x0 ns:organization.organization.acquired_by/ns:business.acquisition.acquiring_company M0 .
  ?x0 ns:organization.organization.acquired_by/ns:business.acquisition.acquiring_company M1 .
  ?x0 ns:organization.organization.acquired_by/ns:business.acquisition.acquiring_company M2 .
  ?x0 ns:organization.organization.acquired_by/ns:business.acquisition.acquiring_company M3 .
  ?x1 ns:people.person.employment_history/ns:business.employment_tenure.company M4
  }