In this question, we need to determine the species that has carbon with a sextet of electrons and can act as an electrophile. Let's analyze the given options:
Based on this analysis, the correct answer is carbocation, since it has a sextet of electrons and typically acts as an electrophile due to its electron-deficient nature.
Carbocations have a carbon atom with a sextet of electrons, making them electron-deficient and capable of acting as electrophiles.


Consider an A.P. $a_1,a_2,\ldots,a_n$; $a_1>0$. If $a_2-a_1=-\dfrac{3}{4}$, $a_n=\dfrac{1}{4}a_1$, and \[ \sum_{i=1}^{n} a_i=\frac{525}{2}, \] then $\sum_{i=1}^{17} a_i$ is equal to
