Option 1 is the correct answer. Statement I claims that there is a large-scale fluctuation of oil flow from oil wells prior to earthquakes. This means that there is an observable change in the rate or amount of oil being extracted from oil wells before earthquakes occur. Statement II explains why this phenomenon happens. It claims that as tectonic stress accumulates to a certain level, the pore pressure within a deep oil-bearing stratum reaches its breaking strength, causing oil to sprout along the oil wells. In other words, the increased pressure resulting from tectonic stress causes the oil to flow more rapidly or in larger quantities from the wells.

Option 2 is incorrect because both statements are true and Statement II is indeed the correct explanation of Statement I.

Option 3 is incorrect because Statement I is true, as supported by observations of oil flow fluctuations prior to earthquakes, however, Statement II is also true and provides the explanation for this phenomenon.

Option 4 is incorrect because Statement I is true and has been observed, but Statement II is also true and explains why this happens.