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Study this image of a geologic time scale.

\begin{tabular}{|c|c|c|c|}
\hline ERA & PERIOD & \begin{tabular}{l}
MILLIONS OF \\
YEARS AGO
\end{tabular} & KEY EVENTS \\
\hline \multirow[b]{2}{}{Cenozoic} & Quaternary & \multirow{5}{}{\begin{tabular}{l}
2.6 \\
66
\end{tabular}} & \multirow{5}{}{\begin{tabular}{l}
Humans evolve \\
Extinction of \\
dinosaurs
\end{tabular}} \\
\hline & Tertiary & & \\
\hline \multirow{3}{}{Mesozoic} & \begin{tabular}{l}
Cretaceous \\
\end{tabular} & & \\
\hline & Jurassic & & \\
\hline & Triassic & & \\
\hline \multirow{6}{}{Paleozoic} & Permian & & \multirow{3}{}{\begin{tabular}{l}
Permian mass \\
extinction
\end{tabular}} \\
\hline & Carboniferous & & \\
\hline & Devonian & & \\
\hline & Silurian & & \multirow{3}{}{\begin{tabular}{l}
Invertebrates \\
become common \\
\end{tabular}} \\
\hline & Ordovician & & \\
\hline & Cambrian & & \\
\hline Proterozoic & \multirow{3}{}{\begin{tabular}{l}
Also known \\
as \\
Precambrian
\end{tabular}} & \multirow{3}{}{2500} & \multirow{3}{}{\begin{tabular}{l}
Earliest life
\end{tabular}} \\
\hline Archean & & & \\
\hline Hadean & & & \\
\hline
\end{tabular}

How long ago did invertebrates become common on Earth?

A. 1.6 million years ago

B. 132 million years ago

C. 410 million years ago

D. 520 million years ago



Answer :

GinnyAnswer
Let's answer the question: "How long ago did invertebrates become common on Earth?"

The key information needed is the time period when invertebrates first became common. According to the geologic time scale, the key event where invertebrates became common is noted during the Silurian period.

From reliable geologic records, it is known that the Silurian period is approximately 410 million years ago.

Thus, the answer is:

410 million years ago.

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