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

What Latin word means an assualt, or a rushing upon?, Context: By the 9th century, Catalan had evolved from Vulgar Latin on both sides of the eastern end of the Pyrenees, as well as the territories of the Roman province of Hispania Tarraconensis to the south. From the 8th century onwards the Catalan counts extended their territory southwards and westwards at the expense of the Muslims, bringing their language with them. This process was given definitive impetus with the separation of the County of Barcelona from the Carolingian Empire in 988.
impetus

Why does PCR have difficulty gaining widespread use?, Context: Thus, the technological ability to detect any infectious agent rapidly and specifically are currently available. The only remaining blockades to the use of PCR as a standard tool of diagnosis are in its cost and application, neither of which is insurmountable. The diagnosis of a few diseases will not benefit from the development of PCR methods, such as some of the clostridial diseases (tetanus and botulism). These diseases are fundamentally biological poisonings by relatively small numbers of infectious bacteria that produce extremely potent neurotoxins. A significant proliferation of the infectious agent does not occur, this limits the ability of PCR to detect the presence of any bacteria.
cost and application