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There are dark regions with numerous craters called impact craters and they cover one-third of the moon. The remainder of the moon is covered by lighter regions which have many ridges and grooves . The ridges are as high as 2000ft and stretch for thousands of miles.</span>
Answer:
Helium
Explanation:
Helium is extracted in a few places in the world, namely USA, Algeria, Russia and Qatar. Helium is abundant in space, where it's produced as a product of the fusion reaction inside stars such as the sun.
Answer:
The correct answer would be D. species.
Natural taxon refers to the group of organisms which exists in nature as a consequence of evolution.
In Linnaeus's system, the only natural taxon is "species".
Species refers to the group of organisms in which two organisms of opposite or appropriate genders can produce a viable offspring.
Antibodies, also called immunoglobulins, are proteins manufactured by the body that help fight against foreign substances called antigens. When an antigen enters the body, it stimulates the immune system to produce antibodies. (The immune system is the body's natural defense system.) The antibodies attach, or bind, themselves to the antigen and inactivate it.<span>
Read more: <span>http://www.scienceclarified.com/Al-As/Antibody-and-Antigen.html#ixzz4YlY105DD</span></span>
