Final answer:
The correct answer is 'was'.
Step-by-step explanation:
The correct answer is b) was.
In this sentence, the action of screaming happened in the past. Since the sentence is in the past tense, the correct form of the auxiliary verb 'to be' is 'was'.
For example, in the given texts, it is mentioned that 'She screamed last night' and 'She did not hear' the screams. Both of these actions happened in the past, so 'was' is the appropriate choice.