After Grenfell, the buildings safety act was extended from 6 years to:

The correct answer is based on the provisions introduced by the Building Safety Act following the Grenfell Tower fire, which tragically highlighted significant issues related to building safety and the enforcement of regulations. In response to the need for more stringent accountability regarding building safety standards, the Building Safety Act extended the limitation period for bringing claims related to construction defects from six years to 15 years for residential buildings.

This extension allows residents or affected parties more time to make claims related to construction defects, thereby addressing the long-term safety concerns that can arise in high-rise residential buildings. This change was part of a broader effort to improve safety standards and ensure that building contractors and developers are held accountable for their work over a more extended period.

Hence, the correct option reflects the aim to enhance the safety and accountability in the construction industry as a direct response to the Grenfell incident.