He’s thinking about joining . . . . . . . . police or . . . . . . . . army. A. the, an B. the, the C. a, an D. a, a

The correct answer is: C. a, an

The word “police” is a common noun, which means that it refers to a general group of people. In this case, the speaker is referring to the police force in general, not a specific police officer. Therefore, the indefinite article “a” is used.

The word “army” is also a common noun, but it is used in a slightly different way. In this case, the speaker is referring to the military in general, not a specific army. However, the military is often referred to as “the army,” so the definite article “the” is used.

Here is a more detailed explanation of each option:

• Option A: the, an
  This option is incorrect because it uses the definite article “the” twice. The definite article is used to refer to specific people or things, and in this case, the speaker is not referring to specific police officers or armies.
• Option B: the, the
  This option is incorrect because it uses the definite article “the” twice. The definite article is used to refer to specific people or things, and in this case, the speaker is not referring to specific police officers or armies.
• Option C: a, an
  This option is correct because it uses the indefinite article “a” once and the definite article “the” once. The indefinite article is used to refer to general people or things, and the definite article is used to refer to specific people or things. In this case, the speaker is referring to the police force in general and the military in general.
• Option D: a, a
  This option is incorrect because it uses the indefinite article “a” twice. The indefinite article is used to refer to general people or things, and in this case, the speaker is not referring to general police officers or general armies.