John is working here since August or has been Can the first sentence also be correct second example only right choice?

The first sentence is incorrect. The second example is the correct choice. Here's why:

* "Since August" implies an action that started in August and continues until now. The present perfect tense is needed for this: "John has been working here since August."

* "Working here" is an action that requires a continuous tense (present perfect).

Here's a breakdown of the correct tenses:

* Present perfect: Used for actions that started in the past and continue to the present.

* Present perfect continuous: Used for actions that started in the past and are still ongoing.

Let me know if you have more grammar questions!