If the broker did not provide the required information on the 1099-B form then it is your responsibily to provide it from your records.  You must have purchased the stock you sold at some time form some amount.   If you do not know the information then your basis is zero and if you owned the stock for more than a year the sale is long term.  

why aren't you able to answer?   contact TD to see if they can provide additional info otherwise select one because we would have no way of knowing which is correct.