HTML：选择大小不同，没有选项

this might be a simple select box problem, but I don't find an answer so far: In my view, there are several multiline select boxes in a row, which are all defined to size=9. I use the size attribute instead of height because it fits the lines (no lines are cutted). Now my problem is that they got different height when they have no options in the select defined.this might be a simple select box problem, but