∵分式13-x的值为正，
∴3-x＞0，
∴x＜3，
故答案为：＜3．
Christmas is ________ becoming a traditional British holiday rather than a Christian one．
A．gradually
B．rapidly
C．slightly
D．necessarily
下列物质在氧气里燃烧，能生成有黑色固体的是（ ）
A．铁丝
B．硫
C．镁条
D．木炭
