Jenny Sells Lemonade by the Street During the Summer Time

Jenny sells lemonade by the street during the summer time.Several other kids also sell lemonade in Jenny's neighborhood.
Refer to the information above.The lemonade stands are perfectly competitive because:

A) the kids get their ingredients from home and don't have to pay for them.
B) it is easy to open a stand and easy to close it down.
C) the table,cups and lemonade pitchers used in the stands are productive resources that are only useful for lemonade stands.
D) the kids do not have regular jobs,so their opportunity costs are zero.