The following question has a sequence of numbers or letters that follow a definite pattern is given. Each questionhas 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.
$$B \otimes Z : 2 \otimes 26 :: E \otimes T : ------$$
$$\sum_{K=1}^{n} : \frac{n(n+1)}{2} :: \sum_{K=1}^{n} K^2 : ---------$$