Your organization sends IoT event data to a Pub/Sub topic. Subscriber applications read and perform transformations on the messages before storing them in the data warehouse. During particularly busy times when more data is being written to the topic, you notice that the subscriber applications are not acknowledging messages within the deadline. You need to modify your pipeline to handle these activity spikes and continue to process the messages. What should you do?

A. Retry messages until they are acknowledged. B. Implement flow control on the subscribers. C. Forward unacknowledged messages to a dead-letter topic. D. Seek back to the last acknowledged message.