Jawless fish were Earth's first

the answer is D

Explanation:

The oldest jawless fish with bone is known from 470 million years ago (Arandaspis). It is similar to the oldest complete fossil of Sacabamaspis from the Late Ordovician. The earliest Ordovician fish seem to be relatives (and perhaps ancestral to) the later group of heterostracans.

jawless fish were earth 's first arthropods

blue stars have the highest surface temp

stellar distances are usually expressed in light-years

the measure of a star's brightness is called magnitude

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