The correct options are
B A group of sellers selling crop seeds in bulk.
C A group of sellers selling vegetables in a place.
The concept of a Sandhai exists, where many sellers meet at a specific time and place to show the goods they have to offer; thus the seeds seller and the vegetable sellers are correct example of sandhai whereas shopping malls are open from day to night and it doesn't have similar shops but a variety of shops, the materials are not made by them, but they are just the sellers and not the producers of the things they sell.