Afriend tells you that her favorite element has an electron configuration of [noblegas]6s24f145d5. which element is it?

             Re  =  Rhenium

Explanation:
                   The electronic configuration of Rhenium is as follow,

                                               [Xe] 6s², 4f¹⁴, 5d⁵

The position of this element in periodic table was found using following trick. 

First of all the period in periodic table was identified by identifying the valence shell in electronic configuration. As the valence shell is 6, so the period in which this element is present is also 6. 

Secondly, as d orbital is identified as (n-1)d so, (6-1)d = 5d, and the number of electrons in d subshell are 5, so in transition elements the group 5 contain this element.

So, tracking period 6, and group 5 in transition elements confirmed Rhenium as the favorite element of my friend.

The answer is b on plato.