Final answer:
Standard time zones are designed to be 15 degrees apart in longitude to correspond with the Earth's 24-hour rotation cycle, but in practice, factors like state and urban area boundaries modify these lines. In North America, for example, time zones are adjusted for practicality. Therefore, the correct answer is C) 15 degrees.
Step-by-step explanation:
Standard time zones are typically established at intervals that reflect the rotational speed of the Earth. The Earth completes one rotation every 24 hours and is divided into 360 degrees of longitude. Accordingly, to align with the 24-hour cycle, each hour of time correlates with 15 degrees of longitude (15×24 = 360). Hence, standard time zones are generally spaced at 15-degree intervals of longitude.
In actuality, these 15-degree time zone intervals need to be adjusted around political and natural boundaries for convenience; for instance, in North America, the boundaries do not follow the longitudinal lines strictly. To maintain practicality and efficiency, they have been drawn to accommodate state lines and keep urban areas within the same time zone when possible. For example, the continental United States has four main time zones (eastern, central, mountain, and western), although not strictly adhering to the 15-degree longitude segments.
Consequently, the correct answer to the original question is 'Standard time zones are spaced at 15° intervals of longitude in North America', which corresponds to option C) 15°. Even though practical application has led to varied boundary lines, the initial spacing is based on the Earth's rotation rate and the desire to keep local solar time roughly around noon when the sun is at its highest point in the sky.
To illustrate this principle, take the eastern standard time zone in the United States, which is five hours behind UTC and approximately 75 degrees west of the prime meridian (5×15 = 75). If it's noon in London (UTC), it corresponds to 7 a.m. in New York. Similarly, Pacific standard time is three time zones, or about 45 degrees longitude away from the eastern standard time zone, representing a 3-hour difference.