Complete the following sentence using the most appropriate option. The…

Concept: Before a singular countable noun, English needs a determiner. The indefinite articles "a" and "an" introduce a first-mention, non-specific member of a class, while the definite article "the" points to something the reader can already identify. Choosing between "a" and "an" depends on the sound that begins the very next word, not on the letter it is spelled with.

Application:

1. The blank is followed by "one-year plan" — a singular countable noun phrase, so a determiner is required.

2. This plan is being introduced for the first time and is not something the reader can already pick out, so an indefinite article is needed rather than the definite "the".

3. The word immediately after the blank is "one-year", pronounced /wʌn-jɪə(r)/. It begins with the consonant glide /w/, even though it is spelled with the vowel letter "o".

4. A consonant sound takes "a", so the sentence reads: The District Manager created a one-year plan to improve sanitation of the city.

Cross-check (sound, not spelling):

Why the other forms do not fit here:

• "an" is used only before a vowel sound, and "one-year" begins with /w/.

• "the" would present the plan as one the reader can already identify, but the sentence introduces it for the first time.

• Using no article would leave the singular countable noun "plan" bare, which standard English does not allow here.