Read the following sentences. The dolphin was swimming swiftly. The dolphin raced to stay with its pod.
Which revision uses a participial phrase to combine these two sentences correctly?

Swimming swiftly was the only way for the dolphin to stay with its pod.

Swimming swiftly, the dolphin raced to stay with its pod.

The dolphin swam swiftly and raced to stay with its pod.

The dolphin raced to stay with its pod by swimming swiftly.