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.

Cognitive psychology is the branch of psychology that studies study internal processes that include perception, attention, language, memory, and thinking.

Cognitive psychology focuses on the way people process information.

Strength of concrete increases with increase in water cement ratio as the strength of the cement is directly proportional to water cement ratio.

Plants are producers, which means they make their own food. Chloroplasts are organelles found in eukaryotic and plant cells that conduct photosynthesis. Chloroplasts absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant.

Plants use energy from sunlight to help make their food, but they need chloroplasts to do it.

Hence, in plants, chloroplasts are necessary for Photosynthesis.

Resistivity :

Resistivity is a measure of the resistance to the flow of electrons. 

Conductivity :

Conductivity is just the inverse of resistivity, σ = 1/ρ, where σ is conductivity and ρ is resistivity.

Example:

Think of a pipe and water, the bigger the pipe, the easier water can flow and thus the lower the resistance.