Final answer:
The Paleozoic Era lasted from about 544 to 245 million years ago, and the time frame representative of the Paleozoic out of the given options is B. 400 million years ago.
Step-by-step explanation:
The Paleozoic Era is known as the era of "old life" and spans from about 544 to 245 million years ago. It is marked by significant events such as the Cambrian explosion, which initiated the era with a diverse array of new life forms, and the Permian extinction, which brought the era to a close.
The Cambrian Period, as the first period of the Paleozoic, saw the evolution of various organisms such as sponges and trilobites around 544-505 million years ago. As time progressed, more complex life forms emerged, including fish, proto-amphibians, and insects.
Therefore, among the provided time frames, the one that is representative of the Paleozoic Era is B. 400 million years ago, as this time falls within the span of the Paleozoic.