“find out”, in bold type in the text, is closest in meaning to

Investigators trying to find out what happened to a Malaysia Airlines jet that disappeared en route to Beijing on Saturday morning were examining the causes of plane crashes: mechanical failure, pilot error, bad weather. But the discovery that two of the passengers were carrying stolen passports also raised the possibility of criminal violence.

(Adapted from “Passport Theft adds mystery of missing Malaysia Airlines Jet”)

GLOSSARY

raised – aumentou, ampliou