after three years, researchers found that parents who took part in risk assessments and received social work referrals, if necessary, had decreased incidences of abuse, fewer reports to child protective services (cps) and better adherence to immunization schedules.

동사에 관한 질문인데요문인데요..

형광색으로 칠한 부분의 논리적 시간적 발생 순서로 보면...

1. took part in / received
2. had decreased
3. found...

즉 위험성 검사와, social work referals를 받은 사람들은 abuse 하는 빈도가 적어졌다는것을 알아냈다.

라고 해석이 됬는데 그렇다면 took part in 대신에 과거완료형으로 써야 맞는거 아닌가여~?

헷갈리네요 ㅠ