In this sentence about singing siblings, choose the noun that best completes the blank: “It so happens that when siblings sing, one of them invariably has a less potent vocal prowess even though both have a similarly commendable ______ base.”

Introduction / Context:
This English vocabulary and collocation question asks you to pick the noun that best combines with “base” to describe the foundation of someone’s singing ability. The sentence contrasts differences in vocal power with a shared underlying foundation. To choose correctly, you must understand how “base” is used metaphorically in the context of art and music.

Given Data / Assumptions:

1) The context is about siblings who sing and their “vocal prowess”.
2) The sentence says “both have a similarly commendable ______ base”.
3) The options are: song, art, common, music.
4) “base” here is metaphorical, meaning foundation or background.
5) We must select the noun that forms a natural and meaningful phrase with “base”.

Concept / Approach:
When dealing with collocations, focus on which word combinations are commonly used by fluent speakers. In the arts, we often talk about someone having a strong “music base”, “musical base” or “musical background”, meaning they have training or grounding in music. Words like “song” and “common” do not normally pair directly with “base” in this way. The correct answer must emphasise a foundation in the field of music.

Step-by-Step Solution:
Step 1: Understand that “base” means foundation or basic grounding. Step 2: Recognise that the context is musical ability, as indicated by “siblings sing” and “vocal prowess”. Step 3: Try “song base”: this sounds unnatural; we usually say “song” as a specific composition, not as a foundational background. Step 4: Try “art base”: this phrase is also uncommon; we might talk about an “artistic base”, but “art base” feels incomplete. Step 5: Try “common base”: although “common base” is a valid phrase in other contexts, it does not specify what the base is about and does not relate directly to music. Step 6: Try “music base”: this matches the context perfectly and easily suggests a solid foundation in music. Step 7: Conclude that “music” is the best noun to complete the phrase “commendable music base”.

Verification / Alternative check:
Read the full sentence with “music”: “It so happens that when siblings sing, one of them invariably has a less potent vocal prowess even though both have a similarly commendable music base.” This clearly conveys the idea that their training or background in music is equally strong, even if one voice is less powerful. No other option provides this precise and natural meaning.

Why Other Options Are Wrong:
“song” refers to an individual piece of music and does not naturally collocate with “base” to mean foundation. “art” is too broad and “art base” is not a common expression. “common” is an adjective, not a noun, so using it before “base” in this context produces an odd and vague phrase that does not mention music at all.

Common Pitfalls:
A frequent mistake is to focus only on whether the word is vaguely related to creativity (like “art”) without checking if the exact phrase is natural. Another pitfall is ignoring the larger context: since the whole sentence is about singing and vocal prowess, the most precise choice must point back to music, not just any general skill. Always test the full phrase out loud to see if it sounds like something a fluent speaker would say.

Final Answer:
The noun that best completes the sentence is music.