  We discuss the level of agreement of a new generation of standard solar
models (SSMs), Barcelona 2016 or B16 for short, with helioseismic and solar
neutrino data, confirming that models implementing the AGSS09met surface
abundances, based on refined three-dimensional hydrodynamical simulations of
the solar atmosphere, do not not reproduce helioseismic constraints. We clarify
that this solar abundance problem can be equally solved by a change of the
composition and/or of the opacity of the solar plasma, since effects produced
by variations of metal abundances are equivalent to those produced by suitable
modifications of the solar opacity profile. We discuss the importance of
neutrinos produced in the CNO cycle for removing the composition-opacity
degeneracy and the perspectives for their future detection.
