for over eighteen hours.中为什么在over前面加个for.for over是固定用法吗

for over eighteen hours.中为什么在over前面加个for.for over是固定用法吗 They waited ( )two hours( )us A for for,B over for 答案是A 但是课本 for twenty-five years和for over twenty-five years在时态用法上一样吗 it's over for for over five Could you come (over)for it?括号填over为什么? He sleeps for nine hours over night的问句 She lay a() for hours thinking over her business. I have been over my homework for three hours 请问：the meeting has been on for over ten mimutes.中为什么加ON? My brother college for over three years.为什么用括号中的.有这种用法吗? come over后面为什么要加个to,还有Come over here.here是个副词,前面能用come over吗