Final answer:
Certain locations in the United States are in "dead zones" where cell phones cannot send or receive messages due to various factors including topography and interference.
Step-by-step explanation:
Certain locations in the United States are in "dead zones" where cell phones cannot send or receive messages due to several factors including topography, distance from cell towers, and interference from buildings or natural obstacles. For example, mountainous terrains or remote rural areas may have limited cell phone coverage due to the difficulty of establishing cell towers in such locations. Similarly, densely populated urban areas with high-rise buildings may experience dead zones caused by signal interference.
Learn more about Cell phone dead zones in the United States