Answer:
O silicon (Si)
Explanation:
-Valence electrons are electrons of the outermost shell which can participate in chemical bonding. ... -As in silicon, four electrons are present in the outermost shell, so silicon has Four valence electrons.
Answer:
4 allopatric
Explanation:
The formation of a new species can occur in several ways. One such process is the separation of two populations of a species geographically. The presence of any geographical barrier may separate the two populations from each other. These populations accumulate variations over time. After several generations, the members of these two populations can not interbreed successfully and are said to be reproductively isolated. The two populations are now two different species. This is called allopatric speciation.
Diffusion across the alveoli
The answer to the question is B.
