Answer:
c. At least once
Explanation:
to compare a reagent that it is in one container and the possible effects that could produce, it it necessary to read and compare with the lab manual. If the name is too long like the organic substances, maybe twice would be better, to avoid mistakes in the spelling.
The comparison of the name is useful, to be aware of the manipulation, the possible reaction with another substance, the toxicity, etc.
Remember in Chemistry substances, security is first.
