Ihave collected so large a body of with animals and plants a cross between different varieties, or between individuals of the same variety but of another strain, gives vigour and fertility to the offspring; and on the other hand, that close interbreeding diminishes vigour and fertility; that these facts alone incline me to believe that it is a general law of nature that no organic being fertilizes itself for a perpetuity of generations; but that a cross with another individual is occasionally—-perhaps at long intervals of time—indispensable. in this sentence from the third paragraph of the passage, what does perpetuity mean? a) gratefulness b) consideration c) a temporary state d) time without end; eternity

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.

what is the statement?

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.