Final answer:
Graphite packing material is the recommended option to use if preformed stem packing is not available for a valve.
Step-by-step explanation:
If preformed stem packing is not available for a valve, the recommended option to use is d. Graphite packing material. Graphite packing material is a commonly used type of valve packing material that offers good sealing properties and can tolerate high temperatures and pressures. It is an effective choice for preventing leaks in valve systems.