Question

Choose the most appropriate form of the given verb:
I _______________ (think) about what you said and I've decided to take your advice.

• A. have thought
  
• B. has thought
  
• C. have been thinking
  
• D. are thinking
  

Answer 1

The correct option is C have been thinking

The present perfect continuous tense (also known as the present perfect progressive tense) shows that something started in the past and is continuing at the present time. Here the action of thinking is continuing to the present. The present perfect continuous is formed using the construction 'has/have been + the present participle (root verb + -ing)'. Hence, Option C is correct.

The rest of the options either indicate that the action has already happened (Options A and B, also, 'has' does not follow 'I'), or it's a continuous action in the present (Option D, and 'are' is plural but 'I' is singular). Hence these options are incorrect.