Complex sentence: Australian Broadcasting Corporation considered the largest contract ever signed between China and Australia, which ensures China a steady supply of LPG fuel for 20 years, and also forms as China's largest supply of relatively "clean energy".
Split into simpler sentences: Australian Broadcasting Corporation considered the largest contract ever signed between China and Australia. This contract ensures China a steady supply of LPG fuel for 20 years, and also forms China's largest supply of relatively "clean energy".