Concept:Salatul Witr is a voluntary prayer known for being offered in an odd number of rak'ahs, including a single rak'ah.
Explanation:The term “Witr” means odd, and this prayer can be performed as one rak'ah.
It is commonly observed after the obligatory Isha prayer and before the time of Fajr.
Other prayers listed, such as Safar, Jama'ah, and Kusuf, are not typically described as a single rak'ah supererogatory prayer.
Therefore, the prayer that fits the description is Salatul Witr.
Answer:C. Witr