What type of investment (stock, mutual fund, index fund, ETF, bond) is a UIT?

Please see this answer from JohnB5677.

The 1099-DIV that you received represents dividends that were received by various mutual funds.  The Mutual Fund and UIT Supplemental Tax Detail includes CUSIPS representing the different mutual funds, and the other information allocates distributions generated by your home vs. other states.

At this time there is not a requirement to enter this on your tax return.

Please see this LINK for more information.

It's not just a 1099-DIV, but also a 1099-INT and a1099-B. 

In  the 1099-B section, Turbo Tax asks me what type of investment it is and forces me to choose from a drop down menu one of the following:

stock

mutual fund, index fund, ETF

bond

options

If there is  not a requirement to enter this on the tax return, then why does TurboTax ask me?