1. You should memorize subject names.

2. He taught us in the first perion.
3. We can find the articles at the CNN website.

Are the English sentences are all grammatical? If there are any mistakes, would you correct them?

1. You should memorize subject names.

2. He taught us in the first period.
3. We can find the articles at the CNN website.

Are the English sentences are all grammatical? If there are any mistakes, would you correct them?

All are correct.

=)

Yes, there are grammatical errors in the sentences. Here are the corrected versions:

1. You should memorize subject names.
2. He taught us in the first period.
3. We can find the articles on the CNN website.

Explanation:
1. The sentence is grammatically correct. The subject names should be memorized.
2. The error in this sentence is the misspelling of "period" as "perion." The corrected version is "first period," referring to a specific class time.
3. The error in this sentence is the use of "at" instead of "on" when referring to a website. The corrected version is "We can find the articles on the CNN website."