oSelection.selectByIndex(index);just count the index of elemnt you wanted to click
i hope it will work
if it wont you can share screent shot of those html element
2nd:: you can try using xpath of the dropdown values as you mentioned it is in form of td
Visit http://www.toolsqa.com/selenium-webdriver/dropdown-multiple-select-operations/ site. You can get clear understanding about the problem you are facing.