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.

TRUE, the compounds are formed as a result of chemical change.

Skimming is the removal of any material or particles that are floating on the surface. Hence, Removal of oil and grease from sewage - waste water is called as skimming.

An atom is composed of three subatomic particles. They are ::

1) Electron (-vely charged particle)

2) Proton (+vely charged particle)

3) Neutron (No charge particle)

Hence, Neutron is the subatomic particle which has no charge.

The repeating units that are used to form the helical DNA structure are called nucleotides.