Commonest aery for cannulation is -
Answer is 'a' i.e. Radial "Aerial puncture and cannulation is performed to measure the Pa02, PaCO2, Sa02 and pH to clarify the acid-base and electrolyte status. Any aery that can be compressed after puncture may be used (but not end-aeries); usually the radial (preferred), brachial, or femoral" - Lee 12/e
Radial
Ulnar
Brachial
Cubital