Which is a Lewis base ?

In the reaction of BeF_(2) with 2F^(Θ) to form BeF_(4)^(-2) , which reactant is the Lewis acid and which is the Lewis base?

In the reaction of BeF_(2) with 2F^(Θ) to form BeF_(4)^(-2) , which reactant is the Lewis acid and which is the Lewis base?

Which is not a Lewis base ?

In the equation I_(2)+I^(-) rarr, I_(3)^(-) which is Lewis base

In the equation I_(2)+I^(-) rarr, I_(3)^(-) which is Lewis base

Which of the following is a Lewis base?