Which of the following directly applies to Hadith ad-Da'if?

"It can be used on certain conditions" directly applies to Hadith ad-Da'if. A Hadith ad-Da'if is a weak tradition or saying of the Prophet Muhammad, and its authenticity is questionable. However, under certain conditions, it can still be used for religious purposes, such as for moral guidance or to gain a better understanding of the Prophet's teachings and practices. However, it cannot be used as evidence in religious legal rulings (fiqh) or to establish a belief in Islam.