In Hemichordates, there is a false notochord known as a stomochord.
A) Proboscis region has the stomochord. Since the stomochord passes through the mouth it is known as 'stomo'chord. Stomo means mouth.
B) Collar region does not have the stomochord.
C) trunk region does not have the stomochord.
D) There is no tail region in the body of hemichordates.
So, the answer is 'proboscis'.