I think it’s A, because all of these are related to fossil fuel somehow.
Answer:
4d orbital.
Explanation:
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In this case, since zirconium's atomic number is 40, we fill in the electron configuration up to 40 as shown below:

Thus, the orbital 4d is partially filled.
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Answer:
(C) The recrystallization solvent should be nonvolatile.
Explanation:
Recrystallization is the separation technique which is used to purify the solid compounds in their crystal or amorphous form.
Some properties follow the recrystallization process as:
The solids are more soluble in hot solvent as compared to the solubility in the cold solvent.
The solvent must have lower boiling point and can be volatile easily.
The solvent should not react with the compound.
The impurities must be soluble in the cool solvent, so that only the pure product crystallizes.
Hence, Answer - C which is not an ideal characteristic.