在摄像机的标准照度下,图像水平清晰度彩色闭路电视监控系统应不低于()。
A.250TVL
B.270TVL
C.350TVL
D.400TVL
参考答案:B
An average of 130000 Chinese _________ abroad for studies every year over the past few years, boosting exchanges in the educational fields
A.was going
B.have been going
C.has been going
D.are going
盥洗前保育员应向婴幼儿强调盥洗的()要求、()要求和注意事项。