In 1869, Russian chemist Dmitri Mendeleev developed the Periodic Table of Elements, a table that arranges the chemical elements into rows and columns. He intentionally left blank spaces for new elements, predicting the discovery of previously unknown elements. This theory proved true when the chemical element gallium (Ga) was discovered in 1875.Choice A is the best answer. The convention being tested is the use of punctuation around noun phrases. No punctuation is needed because the noun phrase “gallium (Ga)” is a restrictive appositive, meaning that it provides essential identifying information about the noun phrase before it, “the chemical element.”
Choice B: No punctuation should be present around a noun phrase consisting of a restrictive appositive (“the chemical element gallium (Ga)”).
Choice C: No punctuation should come between a subject (the noun phrase “the chemical element gallium (Ga)”) and a verb (“was discovered”).
Choice D: The noun phrase “gallium (Ga)” is a restrictive appositive. Setting the phrase off with commas suggests that it could be removed without affecting the coherence of the sentence, which isn’t the case.
✨ Expert's Tip ✨
- An appositive is a noun phrase that clarifies its antecedent.
- An appositive is restrictive when it narrows down the word it modifies. If the restrictive appositive phrase is removed, the sentence will seem like it’s missing something or its meaning will be altered. Therefore, it should not be separated from the rest of the sentence with commas.
