a flight attendant has to be able to size the passengers up 中的“SIZE UP
问题描述：
a flight attendant has to be able to size the passengers up 中的“SIZE UP
答
size up字典中解释就是 to make an assessment of (a person,problem,etc.)
这里就是空乘“仔细观察并做出判断”的意思
911之后,这变成了一项需要的技能,就是为了发现形迹可疑的乘客.