400 videos ____________ already ___________ by Angel for English on YouTube.

Correct answer: have been, uploaded

Explanation:

• Tense and voice needed: The sentence describes a completed action with relevance to the present, and the agent (Angel) is mentioned, so use the present perfect passive: have/has + been + past participle.

• Subject-verb agreement: The subject "400 videos" is plural, so use "have" (not "has").

• Placement of "already": The adverb "already" typically appears between the auxiliary and "been": use "have already been uploaded."

Why the other choices are wrong:

• "are, uploaded": This is present simple passive ("are uploaded"), which indicates a general or habitual state, not a completed action.

• "have, uploaded": This is present perfect active (the subject did the uploading). Because Angel is the agent, the passive form is required: "have been uploaded."

• "are been, uploaded": Ungrammatical. "Are been" is not a valid construction. For ongoing passive use "are being uploaded," and for completed action use "have been uploaded."

Correct sentence (natural word order):

400 videos have already been uploaded by Angel for English on YouTube.