text: Also mixing silica based clay with limestone during cement production leads to release of CO2. సిలికాన్ కూడా లైమ్ స్టోన్ లో కలపడం వల్ల CO2 రిలీజ్ అవుతుంది. This occurs because there is use of energy for this process and releases CO2 gas. Hence both statement two and three are correct, both of them explain statement one.