In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

From what era, once thought devoid of animal life, was evidence of grazer populations discovered?, Context: Some paleontologists suggest that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago. Trace fossils such as tracks and burrows found in the Tonian period indicate the presence of triploblastic worms, like metazoans, roughly as large (about 5 mm wide) and complex as earthworms. During the beginning of the Tonian period around 1 billion years ago, there was a decrease in Stromatolite diversity, which may indicate the appearance of grazing animals, since stromatolite diversity increased when grazing animals went extinct at the End Permian and End Ordovician extinction events, and decreased shortly after the grazer populations recovered. However the discovery that tracks very similar to these early trace fossils are produced today by the giant single-celled protist Gromia sphaerica casts doubt on their interpretation as evidence of early animal evolution.
the Tonian period

Which category contains a 2 year old tree?, Context: To accurately map the Amazon's biomass and subsequent carbon related emissions, the classification of tree growth stages within different parts of the forest is crucial. In 2006 Tatiana Kuplich organized the trees of the Amazon into four categories: (1) mature forest, (2) regenerating forest [less than three years], (3) regenerating forest [between three and five years of regrowth], and (4) regenerating forest [eleven to eighteen years of continued development]. The researcher used a combination of Synthetic aperture radar (SAR) and Thematic Mapper (TM) to accurately place the different portions of the Amazon into one of the four classifications.
2

Where did Luther need to return from?, Context: Luther made his pronouncements from Wartburg in the context of rapid developments at Wittenberg, of which he was kept fully informed. Andreas Karlstadt, supported by the ex-Augustinian Gabriel Zwilling, embarked on a radical programme of reform there in June 1521, exceeding anything envisaged by Luther. The reforms provoked disturbances, including a revolt by the Augustinian friars against their prior, the smashing of statues and images in churches, and denunciations of the magistracy. After secretly visiting Wittenberg in early December 1521, Luther wrote A Sincere Admonition by Martin Luther to All Christians to Guard Against Insurrection and Rebellion. Wittenberg became even more volatile after Christmas when a band of visionary zealots, the so-called Zwickau prophets, arrived, preaching revolutionary doctrines such as the equality of man, adult baptism, and Christ's imminent return. When the town council asked Luther to return, he decided it was his duty to act.
Wartburg