Which option has the incorrect or inappropriate usage of 'grave'?
- AWhen the witness was summoned by the lawyer, he made grave allegations against the accused.
- BThe landlord issued a warning to the tenants that non-payment of rent was a grave matter and would lead to a court case.
- CThey found that all the flowers placed on their mother's grave had withered within a week.
- DThe pet dog could not come to terms with his master's death and went to grave for him, even refusing to eat for several days.