Answer:
Answer is B.
Explanation:
<u>Period is duration of time</u>.
Period can be of a second,minute,hour or of Some years.We will give unit according to the duration of time.In the given options second is most obvious because it is used to measure time.
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.
The process coevolution is a type of relationship between organism wherein they reciprocally affects each others evolution.
Paper, pencils, spoons, trash cans, etc
<span>All organisms mutate their genome automatically when an environment changes, creating new traits and structures.</span>
