Complex sentence: The Doctor tells Sarah their only chance is to stop the androids before they take over the complex, and runs back towards the scanner room, bluffing his way past "Benton" by posing as his duplicate.
Split into simpler sentences: The Doctor tells Sarah their only chance is to stop the androids before they take over the complex. He runs back toward the scanner room, bluffing his way past "Benton" by posing as his duplicate.