Which of the following pairs of 'elements - valency' is correct?

I. Boron - 2

II. Fluorine - 3

Neither I nor II

The correct answer is option 1. Neither I nor II.

Valency refers to the number of bonds an atom of an element can form with other atoms. Let's analyze each statement:

I. Boron - 2
Boron typically forms compounds where it has a valency of 3, not 2. Therefore, statement I is incorrect.

II. Fluorine - 3
Fluorine typically forms compounds where it has a valency of 1, not 3. Fluorine is highly electronegative and tends to gain one electron to achieve a stable electron configuration. Therefore, statement II is also incorrect.

Since neither statement I nor statement II provides a correct pairing of elements and their valencies, the correct answer is option 1. Neither I nor II.