There are a number of issues that you need to overcome when asking the Reader to enter a value in a Text-Box.
1. The Reader may not enter a value, so you will need to check for that.
2. The Reader may enter an invalid value, so you will need to check for that.
eg. you wanted "male" or "female" and they entered "1234"
3. The Reader may enter a value using mixed letter case, so you will need to check for that.
For these reasons it is generally a good idea to use links (or some sort of list based input type) when asking a Reader to select one option from a fixed set of possible choices.