In the context of IPOs, what is underpricing?

a) Underpricing refers to firms tendency to conduct an IPO when they are undervalued by investors.

b) Firms tend to conduct an IPO during cold periods with few IPOs and this causes underpricing.

c) Underpricing refers to the circumstance that on average the initial return from the offer price to the first closing market price is positive.

d) Underpricing refers to newly-listed firms tendency to be undervalued on the market in the first few years after their IPOs