Breaking strength is determined by cutting a test strip taken from an area that is __________ to the elements, which __________ by 4-6 inches.

Breaking strength refers to the maximum stress that a material can withstand before failing or breaking. The correct answer indicates that breaking strength is determined by cutting a test strip from an area that is exposed to the elements. When materials, especially fabric used in aircraft covering, are exposed to environmental conditions—such as UV light, humidity, and temperature variations—they may undergo degradation affecting their strength.

In this context, if an area is exposed to the elements, the effects of environmental degradation can lead to a decrease in its breaking strength. The exposure causes wear and tear, which weakens the fibers and can lead to a lower performance when tested for strength. Therefore, measuring breaking strength on a strip from this exposed area helps in understanding how the fabric performs under real-world conditions, taking into account the deterioration caused by environmental factors.

Some other choices present conditions that either protect the material from the elements or incorrectly imply a variation that does not directly correlate with the actual performance measurement. Understanding the impact of exposure on material strength is crucial for ensuring safety and reliability in aircraft operations.