The government has announced, "Taxes will be raised":

Answer: Option C

The sentence is in direct speech: "The government has announced, 'Taxes will be raised.'"

To convert it into indirect speech, we observe the tense of the reporting verb — "has announced", which is in the present perfect tense.

Rule: When the reporting verb is in the present, present perfect, or future tense, the tense in the reported speech does not change.

Since "will be raised" is a future tense construction and the reporting verb is not in the past, we keep "will be raised" as it is.

Option C correctly follows this rule: "The government has announced that taxes will be raised."

Option A is incorrect because it unnecessarily changes "will" to "would", which should only occur when the reporting verb is in the past tense.

Option B is grammatically incorrect because "would raised" is not a valid construction — it should be "would be raised".

Option D is incorrect because it omits the conjunction "that", making the sentence grammatically informal and incomplete for reported speech.

Therefore, the correct answer is Option C.