thE Author FoCusEs primArily on ______.
A．two CompEting sCiEntiFiC moDEls ConCErning thE sun's mAgnEtiC FiElD
B．An ovErviEw oF somE rECEnt sCiEntiFiC DEvElopmEnts in solAr physiCs
C．thE rEAsons why A proBlEm in solAr physiCs hAs not yEt BEEn solvED
D．thE DiFFiCultiEs involvED in linking tErrEstriAl ClimAtE with solAr ACtivity