Complex sentence: As Anna had been claiming that she wanted to learn De Souza Enterprises from the ground up, Carl agreed to let her take out one of the company trucks for a test ride, neglecting to tell her that he'd only half-filled the fuel tank.
Split into simpler sentences: As Anna had been claiming that she wanted to learn De Souza Enterprises from the ground up, Carl agreed to let her take one of the company trucks for a test drive. He neglected to tell her that he'd only half-filled the fuel tank.