Humans have an internal skeleton made of bones because it provides better protection for our vital organs and allows for more efficient movement. An internal skeleton also allows for growth and flexibility as bones can grow and adapt as we age. Insects have an external skeleton, known as an exoskeleton, which provides protection but limits their growth and movement as they need to molt and shed their exoskeleton to grow. Having an internal skeleton also allows humans to have a larger body size and more complex internal systems compared to insects with external skeletons. **

The legality of a flight altitude depends on various factors such as air traffic control regulations, airspace restrictions, and the specific flight plan. Pilots must adhere to the altitude restrictions set by air traffic control and comply with any airspace regulations in the area they are flying. Additionally, the aircraft's performance capabilities and the weather conditions also play a role in determining the legal flight altitude. Therefore, without specific details about the flight and the regulations in place, it is not possible to determine the legality of the flight altitude. **

The moon's altitude refers to its angular distance above the horizon. The moon's altitude changes throughout the night as it moves across the sky. At its highest point, the moon's altitude can reach around 90 degrees, which means it is directly overhead. The moon's altitude is an important factor for astronomers and navigators when determining its position in the sky. **

Altitude difference refers to the vertical distance between two points, typically measured from sea level. It is the difference in elevation between the highest and lowest points in a given area. Altitude difference is an important factor in determining the topography and terrain of a region, and it can have significant effects on weather patterns, ecosystems, and human activities such as agriculture and transportation. **

The muscles that perform external rotation of the shoulder are primarily the Infraspinatus and Teres Minor muscles. These two muscles are part of the rotator cuff group and are responsible for rotating the shoulder joint outward. Strengthening these muscles is important for maintaining shoulder stability and preventing injuries. **

Clouds float at various altitudes depending on their type. For example, cirrus clouds can be found at high altitudes of 20,000 feet or more, while cumulus clouds typically form at lower altitudes around 6,500 feet. Altostratus clouds are found at mid-level altitudes around 6,500 to 20,000 feet. Overall, clouds can be found floating at different altitudes in the Earth's atmosphere, ranging from low to high levels. **

The altitude at which one can survive varies depending on factors such as individual health, acclimatization, and the rate of ascent. Generally, humans can survive at altitudes up to around 18,000 feet (5,500 meters) without experiencing severe altitude sickness. However, prolonged exposure to altitudes above 26,000 feet (8,000 meters) without supplemental oxygen is not sustainable for most people due to the lack of oxygen at high altitudes. It is important to acclimatize properly and be aware of the symptoms of altitude sickness when ascending to high altitudes. **

The altitude at which one dies can vary depending on individual factors such as age, health, and acclimatization to high altitudes. However, most people cannot survive for long periods above 26,000 feet (8,000 meters) without supplemental oxygen due to the lack of sufficient oxygen in the air. At extremely high altitudes, the lack of oxygen can lead to altitude sickness, hypoxia, and eventually death. **