The correct option is B Application of iron and magnesium to promote synthesis of chlorophyll.
If a pulse crop possesses premature yellowing of leaves and decrease in yield, it is the symptoms of chlorosis i.e., reduction of chlorophyll then application of magnesium and iron to promote synthesis of chlorophyll and to obtain maximum seed yield. Magnesium is an important part of the ring structure of chlorophyll molecule and its deficiency causes chlorosis and premature leaf abscission. In iron deficiency also,the leaves become chlorotic because iron is required for the synthesis of some of the chlorophyll-protein complexes in the chloroplast. Hence option B is correct.