The correct answer is option 4: Market of safe securities.

The term "gilt-edged market" in India refers to a market where safe and low-risk securities are traded. These securities are considered to be of high quality and are issued by the government or highly reputable entities. In this market, investors generally have a low risk of default or loss of their investment.

The alternative options mentioned (gold and silver, platinum, and shares of companies on the basis of which the Sensex is calculated) are not accurate definitions of the gilt-edged market.

Gold, silver, and platinum are precious metals that are traded in separate commodity markets.

Shares of companies on the basis of which the Sensex is calculated are traded in the stock market, also known as the equity market. This market carries a higher level of risk compared to the gilt-edged market.

In conclusion, the gilt-edged market in India refers to a market of safe and low-risk securities issued by the government or highly reputable entities.