Answer:
A
Explanation:
A covalent bond consists of the mutual sharing of one or more pairs of electrons between two atoms. These electrons are simultaneously attracted by the two atomic nuclei. A covalent bond forms when the difference between the electronegativities of two atoms is too small for an electron transfer to occur to form ions.
Answer:
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Explanation:
It helps to ascertain the number of living beings on Earth. More than one million of species of plants and animals have been discovered and classified so far. It aims to classify the living organisms. Millions of organisms are classified scientifically in categories, which helps to have a better understanding
Placenta
It also does not allow the maternal and fetal bloodstreams to mix
