Final answer:
The key segregation of duties for the revenue process is to have different parties performing distinct functions.
Step-by-step explanation:
In the revenue process, segregation of duties is important to prevent fraud and errors. As for the options mentioned, A) preparing shipping orders and preparing bills of lading, and C) performing the shipping and billing functions, both involve the same party having control over multiple functions. This lacks proper segregation of duties. On the other hand, B) performing the credit and billing functions, and D) receiving cash and adjusting accounts receivable, involve different parties performing distinct functions, which ensures proper segregation of duties.