Answer: C) of
He was cured of the disease. ✅
cure of = the standard collocation for diseases/illnesses
➡️cure of → for diseases, problems: cured of cancer
➡️cure by → used for the method/doctor: cured by a doctor
➡️cure with → used for the treatment: cured with antibiotics
➡️cure from → not used for diseases
of = what you had
by/with = how it was treated