Answer:

Explanation:
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In this case, according to the required half-reaction, we start by setting it up from bismuth (V) oxide ion to bismuth (III) ion:

Thus, next realize that the oxidation state of Bi in BiO3^- is 5+ because oxygen is 2- (-2*3+x=-1;x=-1+6;x=+5), so we obtain:

Thereafter, we realize three water molecules are needed on the right in order to balance the oxygens and consequently 6 hydrogen atoms on the left to balance hydrogen:

Now, since the balance is is basic media, we add six molecules of hydroxide ions in order to produce water with the hydrogen ones:

Then, we accommodate the waters to obtain:

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The correct answer among the choices given is option A. Eustachian, Pharynx, Bronchi are structures that ensembles a tube. The Eustachian tube is a narrow passage from the pharynx to the middle ear. Pharynx is a passageway leading from the oral and nasal cavities to the larynx and the esophagus. Lastly, bronchi is an airway in the respiratory tract.
A pi bond is a bond formed by the overlap of orbitals in a side-by-side fashion with the electron density concentrated above and below the plane of the nuclei of the bonding atoms. ... Three sigma bonds are formed from each carbon atom for a total of six sigma bonds total in the molecule.