A 65-year old presents to the medical clinic complaining that he is not able to hold items in his right hand. He is an electrician and noticed that for the past 4 weeks his hand has become stiff and rigid. He denies any trauma to the hand. His hand was perfectly fine before and he has no idea what has happened. His past medical history reveals he had a left inguinal hernia repair done 12 years ago and several skin lesions excised from his face. He does have hypercholesterolemia for which he takes a statin. He drinks alcohol, smokes and uses marijuana regularly. He has no allergies. After seeing his hand, the first test of choice is?
A. EMG studies
B. Nerve conduction study
C. Chest x-ray
D. Muscle biopsy