一等锁两起算边之间的锁段长度一般为()左右,锁段内的三角形个数一般为()个。
参考答案:200公里、16~20
Many a student ____ going to have themselves ______ in the hospital.
A.is ; to examine
B.are ; examine
C.is ; examined
D.are ; examining
载荷小而且平稳,应选用滚子轴承。