Which trait would best indicate that a particular arthropod was a member of subphylum chelicerata? jointed appendages sexual reproduction terrestrial lifestyle two body segments compound eyes?

The answer is two body segments.

The trait that would best indicate that a particular arthropod was a member of subphylum chelicerata is that it possess two body segments instead of three; a fused head and thorax (cephalothorax), and an abdomen (opisthosoma). Their segmented body with jointed limbs is covered in a cuticle made of chitin and proteins. The subphylum chelicerata includes the arachnids, horseshoe crabs, scorpions and related forms.