”这个字的笔顺是什么?“是最好的答案。
另外,一般中文中不会有“什么”和“吗”,两个疑问词同时出现,所以问题的问法应该是:“这两句话哪句是对的?”或者“这两句话有对的吗?” And basically, you couldn't use two question words in one sentence in Chinese, therefore the right way to ask "which one of these two sentences is correct?" should be in these ways “这两句话哪句是对的?” or “这两句话有对的吗?”