a question mark hang over something
US /ə ˈkwes.tʃən mɑːrk hæŋ ˈoʊ.vər ˈsʌm.θɪŋ/
UK /ə ˈkwes.tʃən mɑːrk hæŋ ˈoʊ.vər ˈsʌm.θɪŋ/

1.
懸而未決, 存在疑問
a feeling of doubt or uncertainty about something
:
•
A question mark hangs over the future of the company.
公司的未來懸而未決。
•
His involvement in the scandal still has a question mark hanging over it.
他是否捲入醜聞仍懸而未決。