What is the correct answer?

[Abdullah al]

If your site is not appearing in Google search results because of some unethical SEO practices in the recent past, _________________.
a. Abandon and close your website permanently.
b. Modify the page contents, make them useful and relevant to the human users, and request Google to reconsider your site.
c. Start a PPC campaign to get your site included in the sponsogreen results.
d. it is better to discontinue the website and shift your webpages to a fresh website with a new domain name.

[Jake]

B

Sites might be de-indeed for 6 to 12 months after ignoring warnings of "Unatural link patterns"

Apologizing and demonstrating intentions to set things right helps in getting back into the index.

[Bhanu]

It is

b. Modify the page contents, make them useful and relevant to the human users, and request Google to reconsider your site.

[Charles Williams]

You can modify the page contents and request Google to reconsider your site. It's the best way to get rankings in Google search results.

[Gaurav]

First you need to make your question clear. what kind of unethical practices was applied to that site? is it on page or off page
if you want to continue with the same site then the correct answer is b but you must know which penalty Google apply to your site. if this penalty is related to content then you need to change it and if this penalty is related to link building then you need to remove such links to make your site good in the eyes of search engines.