Definition: having no answer or solution Level: C1
关于他失踪的谜团仍未解开。
The mystery surrounding his disappearance is still ___unsolved.
因此，许多问题仍未解决。
Consequently, a lot of problems remained ___unsolved.
尽管调查了多年，这起罪行仍未破案。
Despite years of investigation, the crime remains ___unsolved.
