To prevent blood flowing back after each heartbeat. They ensure that the blood flows only in one direction (back to the heart).
There are several costs associated with using wind turbines to generate electricity.
<u>Explanation:</u>
Using wind turbines to generate electricity comes with the cost of installation of the turbines. A suitable site for installation has to be selected and windmills of the required height are installed. Cost of maintenance is another cost associated with the usage of wind turbines.
The windmills are subjected to several environmental factors like rainfall, sunlight etc. These can cause damage to the windmills. Thus a regular maintenance of the turbines is essential.
Cost of procuring appropriate land for installation of wind turbines is another associated cost. Locations apt for harnessing wind energy are limited. Moreover the windmills have to be set up across a large area to produce energy in a decent scale.
The concentration and size of boxes the same at all locations is not the same size. The deaths due to cholera vary depending upon the location. The relative sizes represents that died at that certain spot.
Explanation:
The black boxes represent relative numbers of death due to cholera. Cholera is referred to as a disease of poverty because of the lack of social development in the areas in which it occurs. Crowded camps are fertile ground for a cholera outbreak. Other humanitarian crises including flooding and earthquakes, civil unrest or war that causes disruption of water and sanitation systems.
