A sequence of numbers or letters that follow a definite pattern is given. Each question has a blank space. This has to be filled by the correct answer from the four given options to complete the sequence without breaking the pattern.
$$\sqrt{1 + \sqrt{15}}, \sqrt{3 + \sqrt{13}}, ------------, \sqrt{10}$$
$$\frac{2}{3}, \frac{8}{9}, \frac{26}{27}, \frac{80}{81}, --------, \frac{728}{729}$$