In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

What did the principle of inertia do for general relativity?, Context: The concept of inertia can be further generalized to explain the tendency of objects to continue in many different forms of constant motion, even those that are not strictly constant velocity. The rotational inertia of planet Earth is what fixes the constancy of the length of a day and the length of a year. Albert Einstein extended the principle of inertia further when he explained that reference frames subject to constant acceleration, such as those free-falling toward a gravitating object, were physically equivalent to inertial reference frames. This is why, for example, astronauts experience weightlessness when in free-fall orbit around the Earth, and why Newton's Laws of Motion are more easily discernible in such environments. If an astronaut places an object with mass in mid-air next to himself, it will remain stationary with respect to the astronaut due to its inertia. This is the same thing that would occur if the astronaut and the object were in intergalactic space with no net force of gravity acting on their shared reference frame. This principle of equivalence was one of the foundational underpinnings for the development of the general theory of relativity.
one of the foundational underpinnings

What might be pleasing to look at?, Context: Lighting fixtures come in a wide variety of styles for various functions. The most important functions are as a holder for the light source, to provide directed light and to avoid visual glare. Some are very plain and functional, while some are pieces of art in themselves. Nearly any material can be used, so long as it can tolerate the excess heat and is in keeping with safety codes.
Lighting fixtures

The UN generally refuses to make Israel's actions?, Context: Meanwhile, Begin's government provided incentives for Israelis to settle in the occupied West Bank, increasing friction with the Palestinians in that area. The Basic Law: Jerusalem, the Capital of Israel, passed in 1980, was believed by some to reaffirm Israel's 1967 annexation of Jerusalem by government decree, and reignited international controversy over the status of the city. No Israeli legislation has defined the territory of Israel and no act specifically included East Jerusalem therein. The position of the majority of UN member states is reflected in numerous resolutions declaring that actions taken by Israel to settle its citizens in the West Bank, and impose its laws and administration on East Jerusalem, are illegal and have no validity. In 1981 Israel annexed the Golan Heights, although annexation was not recognized internationally.
recognized internationally