I will have an exam soon. It is said that what type of mobile phone card with signal shielding device is the best? Please make a detour to persuade me not to cheat. thank you

The standard configuration of mobile phone signal shielding can shield all mobile phone signals and 2.4G WIFI signals of China Unicom and China Telecom. The shielding effect of these signals is the same, so it makes no difference no matter what mobile phone card is used. Some people will say, then why are the distances between mobile phones, China Unicom phones and telecom phones different? That's because the location, density and power of the base stations of these three operators are different, so the signal strength of mobile phones presented is different, resulting in different shielding distances.