Answer:
D. She couldn't believe it; she'd forgotten the cake
Step-by-step explanation:
This is the sentence that would most likely end with an exclamation mark (!). An exclamation mark is a punctuation symbol that is meant to represent extreme surprise, disbelief, anger, or any other very intense emotion. It signals a change in intonation and volume. In this case, the last sentence would most benefit from it as it would express the woman's disbelief.