The thickness of the ice cap of the Earth's Antarctic reaches 4.8 kilometers. The pressure of the ice layer can reduce the freezing point of the water. The temperature at the bottom of the ice cap can allow the existence of liquid water. The radar wave can detect the liquid water below the Antarctic ice cap. And it receives reflected echoes. Electromagnetic waves of different frequencies have different penetrating capabilities. The lower the frequency, the greater the depth of penetration. When the electromagnetic waves are transmitted down through the ice, they will be reflected back at the interface between different substances. Waves, such as the interface between ice and bedrock, water-containing sediment, and liquid water bodies, will all reflect echoes, and the radar will advance along the flight track to continuously measure and obtain underground images. Which of the following statements is consistent with the original:. ['Radar is the most basic means of detecting underground objects.', 'The frequency of electromagnetic waves is inversely proportional to the penetration depth.', 'There must be life at the bottom of the Antarctic ice sheet.', 'The reflection of the electromagnetic wave is the same between different materials.']