This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
In a child with absent thumb, radial detion of wrist, bowing of forearm, which of the following investigation will not be useful? 
Select and explain. 
A. Bone marrow examination, B. Karyotyping, C. Platelet count, D. 2D ECHO
B: Karyotyping
Answer: B: Karyotyping 
Explanation: Absent thumb present in Fanconi anemia diagnosed by bone marrow In TAR syndrome diagnosed by platelets count Holt Oram syndrome diagnosed by 2D ECHO (Absent thumb and radius associated with ASD)