What is ungrammatical about this sentence?
Jack believed that Bob said that Nancy saw Bill drove fast yesterday.
At the moment I have found out that the main verb,believed, is tensed, and the suboordinate clauses are complements of the verb. However, I am struggling with finding a mistake in this sentence. The only thing I can think of right now is that the word ''that'' is optional in tensed subordinate clause complements, but I am not sure if that's the actual error
