Would a linguist find the following sentence to be a valid English sentence grammatically?

he belief that Mary kissed Bill is mistaken.
OPTIONS:
- unacceptable
- acceptable
unacceptable
Skulle en lingvist finna följande mening vara en giltig engelsk mening grammatiskt? Han tror att Mary kysste Bill är fel. ALTERNATIV: - oacceptabelt - godtagbart
Would a linguist find the following sentence to be a valid English sentence grammatical? He thinks Mary kissed Bill is wrong. ALTERNATIVES: - unacceptable - acceptable
oacceptabelt
unacceptable