premise: How to substitute for mustard seed<br>Use prepared horseradish to add spice. Prepared horseradish is made by combining ground horseradish with vinegar, and sometimes other spices, to form a sauce. You can get it from your local supermarket.
hypothesis: Prepared horseradish always has the same spices. 
reason: It said that you sometimes add other spices. So the spices can be different and you may not always use the same one. Because of that the statement is incorrect.