In direct speech, the words of the speaker are quoted exactly as they were spoken. However, when we report someone's words in indirect speech, we usually change the tense of the verb to reflect the time frame in which the reported speech is being spoken or the action is taking place.

The correct answer to the question is option 'B', which states that a direct speech is usually reported in the past tense in indirect speech. This means that when reporting someone's words, we generally change the tense of the verb from the present tense to the past tense.

Example:
Direct speech: "I am going to the party tonight."
Indirect speech: She said that she was going to the party tonight.

Explanation:
In the direct speech, the speaker says, "I am going to the party tonight." This sentence is in the present tense as it reflects the speaker's current action or plan. However, when we report this sentence in indirect speech, we change the tense of the verb to the past tense. So, in the indirect speech, we say, "She said that she was going to the party tonight." The verb "am" in the direct speech changes to "was" in the indirect speech to reflect the past tense.

Changing the tense from present to past in indirect speech helps to indicate that the reported speech is being spoken in a different time frame from the actual speech. It allows us to accurately report what someone said without confusing the timeline of events.

Therefore, to accurately report someone's words in indirect speech, we generally use the past tense to reflect the time frame in which the reported speech is being spoken or the action is taking place.