Questions

Brazil is one example of a closed economy in the given options. 

A closed economy is one that has no trade activity with outside economies. A closed economy is self-sufficient, which means no imports come into the country and no exports leave the country. A closed economy's intent is to provide domestic consumers with everything they need from within the country's borders.

Tropical rainforests are such rainforests that occur in the region of tropical rainforest climate where there is no dry season and it remain hot and wet.Tropical evergreen rainforest biome provides optimum environmental conditions for the growth of plants and animals because it experience heavy rainfall and high temperature, and extend between 10° N and 10° S latitudes. The biome Tropical rain forests are of mega thermal type because the organisms are adapted to high temperature and wet and humid condition. The maximum development of this biome has taken place in South America, lowland regions in Africa, and the islands off of Southeast Asia, Central America and parts of Australia.

Helium has the lowest freezing point of all the elements. When coming to metals, mercury has the lowest freezing point of all the metals.

Yes, Carbon disulfide is prepared by heating sulfur and charcoal. 

S2 + C ----> CS2

Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.

About 150 - 200 species of plant, insect, bird and mammal become extinct every day or 24 hrs.

This is not an accurate but an estimation by U.N. Convention on Biological Diversity and Global Extinction Rates. It is also said that current extinctions were 'up to 100 times higher than the background rate.'