Complex sentence: Acupuncture constitutes a key component of traditional Chinese medicine (TCM), which has been described as "fraught with pseudoscience", with no valid mechanism of action for the majority of its treatments.
Split into simpler sentences: Acupuncture constitutes a key component of traditional Chinese medicine (TCM), the validity of which has been disputed for some time. Acupuncture has been described as "fraught with pseudoscience", with no valid mechanism of action for the majority of its treatments.