We could need ten years to stop any asteroid hitting Earth

NASA and other agencies simulated an asteroid impact scenario, revealing that current technology cannot prevent an asteroid from hitting Earth if detected too late. Experts suggest a minimum of five to ten years is needed to study and mitigate such threats. Legislation requires NASA to track 90% of large Near Earth objects by 2021, but only 40% have been tracked. Potential mitigation strategies include using explosives, lasers, or spacecraft to alter an asteroid's path, all requiring years to implement.

What factors would need to be studied about an asteroid to effectively plan for its threat?

What percentage of Near Earth objects 140 meters or larger had NASA tracked by 2021?