Which of the following plants is used to extract the blue dye?

1.  Trifolium

2.  Indigofera

3.  Lupin

4.  Cassia


(b) Indigofera tintoria and T suffruticoga are the two plants belonging to the family-Fabaceae that produce blue indigo dye.
The other options are incorrect as
Trifolium is used as fodder.
Lupin is an ornamental plant.
Cassia is a shrub usually grown on the road side as an ornamental plant.