Answer:
Areas where the air is warmed often have lower pressure because the warm air rises. These areas are called low pressure systems. Places where the air pressure is high, are called high pressure systems. A low pressure system has lower pressure at its center than the areas around it.
Explanation:
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South African people are vaccinated with Yellow fever. First, SA is strict in the implementation proof of vaccination in travelers coming in the country. The vaccination card must show vaccination at least ten days prior to travel. This is to prevent reintroduction of the disease to SA people. Second, In the list of Center for Disease Control, South Africa is not included in the countries with an endemic Yellow fever which means that the disease is wiped out if not controlled through vaccination.
To help the nervous system and brain develop.
External skeleton is the correct answer. Hope this helps out !