This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
Rigid esophagoscopy is not done in -a) Cervical spine rigidity b) Aortic aneurysmc) Carcinoma esophagus d) Esophageal webe) Lung abscess 
Select and explain. 
A. ac, B. ab, C. ad, D. bc
B: ab
Answer: B: ab 
Explanation: Contraindications of esophagoscopy (rigid type):

Trismus
Aneurysm of aorta
Receding mandible
Advanced heart, liver, kidney diseases (relative contraindication).
Diseases of cervical spine, e.g. cervical trauma, spondylitis, TB, osteophytes, kyphosis, etc.