Which group of sounds is known to be continuous and can be held without distortion?

The group of sounds identified as continuous and capable of being held without distortion is indeed the /sh/ and /f/ combination. Continuous sounds can be prolonged smoothly without any interruption, meaning they can be sustained as long as air is exhaled without the need for a complete closure of the vocal tract.

In this case, both /sh/ (as in "ship") and /f/ (as in "fish") are examples of fricative consonants, where the airflow is partially obstructed, creating friction. This allows these sounds to be pronounced continuously, making them suitable for exercises that involve sound manipulation or blending.

By contrast, the other choices consist of sounds that require complete closure of the vocal tract or significant movement within the mouth for their articulation, causing them to be shorter and non-continuous.