Survey Automatically attaching to an Opportunity

Hello folks,

Problem: When i create a new Opportunity, one of my Surveys get automatically attached to the Assessments in the Opportunity. I have no idea why is that happening?

What I want it, it should not come automatically, rather it should only come when selected from the selction list, like any other survey.

What should I do..? please suggest asap.

Thanks,

Abhi