The question requires us to choose among the elements Fr, Ar, Bi and Be which one would lose its valence electrons faster.
To answer this question, we need to take a look at the elements electronic configurations:
Fr: [Rn] 7s1
Ar: [Ne] 3s2 3p6
Bi: [Xe] 4f14 5d10 6s2 6p3
Be: 1s2 2s2
Note that, considering the elements given, Fr is the one that has only one valence electron; Ar is a noble gas and has 8 electrons in its valence shell, Bi is a metal with 5 valence electrons (and tends to receive electrons instead of losing them) and Be is a small atom with 2 valence electrons. Also, looking at these elements position in the periodic table, we can see that Fr should present a bigger atomic radius compared to the other elements (remember that the atomic radius tends to increase from top to bottom and from right to left in the periodic table).
Due to the number of valence electrons and to the size of the atom, Fr is the element that would lose its valence electron faster considering the group of elements given.