In the following question, out of the four alternatives, select the alternative which will improve the bracketed part of the sentence. In case no improvement is needed, select "no improvement". I (have been advocate) moderation in daily physical exercise for nearly half a century in all my writings and books.?

Option 3 : have been advocating

The correct answer is 'have been advocating'

• According to grammar, we use the present perfect continuous tense when something started in the past and is continuing at the present time. The present perfect continuous is formed using the construction has/have been + the present participle (root + -ing).
• 'For nearly half a century' shows that the completion of the time. 
• The action that is 'advocating moderation' is still continuing in the present.
• Let's see an example-
  • I have been reading War and Peace for a month now.

So the correct sentence is- I have been advocating moderation in daily physical exercise for nearly half a century in all my writings and books.