You are assigned as Project Manager to Project that is in execution phase. What you will do avail the opportunity or refuse?

Your a lucky to have the option to refuse. I don't think that this available in most cases. I will assess the project team, the project plan, and the project current status compared to the approved plan. I will discuss my findings with the stakeholders and formally present my views and take over based on my report.

I agree to what Mohamad Tohamy mentioned. And that's exactly what's recommended by PMBOK too. 

Infact, it's a boon in disguise to a PM to avail the chance in detailing the facts (for ex: is there a WBS created.. and have the activities been listed, are estimates calculated with team's buy-in, etc etc). 

Collect all the planning documents and see all the timings and review the milestones and start review all the tasks by see who have to do what.

it depends upon the opportunity which is determinal to profit (favorable) and do not use if favorable.if determintal and unfavourable refuse it

One needs to understand the current project status and create a project report with further plan and actionable. All the identified risks and foreseen risks to be analysed with team members and identify the controls if any.This needs to be presented to Business Team / project Sponsor before taking up the project. Once approved, then we can proceed though it will be challenging task.