Best answer gets brainliest

C) Mercury based thermometer

Explanation:

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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~ trueboss72