The factor that is responsible for the phenomenon of the blood group B being almost absent in Native Americans whose ancestors arrived in very small numbers about 10,000 years ago would be called the 'founder effect'.
Answer: True
Sometimes the use of condoms can't prevent STIs(sexually transmitted infections) because of the manufacturer fault. STIs that caused by lice is not protected too because the condom doesn't cover hair. Other than that, a condom provides a good physical barrier that prevents diseases that transmitted body liquid.
Answer:
A.The hole in the ozone layer
Explanation:
• Montreal protocol is an international treaty that was signed to control the use of substances that are resulting in the depletion of the ozone hole.
This treaty was signed in the year 1987 and became effective form 1989.
• Since the time that this treaty has come into force, there has been a significant improvement in the ozone hole that was observed over Antarctic as it's size has decreased.
• This improvement has been possible because the treaty helped to phase out chemicals such as chlorofluorocarbons, carbon tetrachloride, etc. that are responsible for ozone hole depletion.
Answer:
The coral reefs of the Caribbean are thought to be under threat
Explanation:
Overfishing threatens over 60 percent of Caribbean coral reefs. Declines in coral cover and increases in algal cover have been observed across the region. This analysis identified about one-third of Caribbean reefs at high threat from overfishing pressure and about 30 percent at medium threat.
