Select the correct active voice of the given sentence.

The watchman has been bitten by a stray dog.

A stray dog has bitten the watchman.

The correct active voice of the given sentence "The watchman has been bitten by a stray dog" is A stray dog bit the watchman.

The passive voice of the sentence is "The watchman has been bitten by a stray dog." This sentence is in the present perfect tense, which is used to describe an action that has happened in the past and is still relevant to the present. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "the watchman" and the main verb is "bite." The past participle of "bite" is "bitten." So, the passive form of the sentence is "The watchman has been bitten by a stray dog."

The active voice of the sentence is formed by putting the subject of the passive sentence before the verb and removing the word "by." In this case, the subject of the passive sentence is "a stray dog," and the verb is "bite." So, the active form of the sentence is "A stray dog bit the watchman."

The other options are incorrect because:

• A watchman has bitten the stray dog." This sentence is in the active voice, but the subject of the sentence is "a watchman," which is not the one performing the action.
• A stray dog is biting the watchman." This sentence is in the present continuous tense, which is used to describe an action that is happening now but is not finished. However, the action of biting the watchman is not happening now.
• A stray dog has bitten the watchman." This sentence is in the simple past tense, but the action of biting the watchman is still relevant to the present.