分流道的表面粗糙度一般为1.6µm即可,这样能使熔融塑料的冷却皮层固定,有利于保温。
参考答案:对
—Lily dances so well . Where was she trained?
—She learns all by herself .She _______goes to any training class.
A.usually
B.often
C.even
D.never
某二叉树中度为2的结点有18个,则该二叉树中有______个叶子结点。