cases had fallen to such a low

cases had fallen to such a low when crossing the street,the lady ------to the groundAfalls Bfell Chas fallen D had fallen had fallen asleep为什么不对? direct cases to Marie is very wet.She ____ in the river:can have fallen B:had to fall C:must have fallen D:needn't to fall Marie is very wet.She ____ in the river.this morning.A:can have fallen B:had to fall C:must have fallen D:needn't to fall He had ---- early and had slept badly答案给的是gone to bed,为什么不可以是fallen asleep The unemployment rate in this district (has fallen) from6%to 5%in the past two years为什么括号内不能是 had fallen when I ran out to find that a big tree had fallen down 最前面的when为什么要去掉 we had our picnic next to a fallen tree in the forest.翻译,语句通顺（正常一点儿） they moved to the new city in 1998,since then they ___ each othera:have been in love withb:have fallen in love withc:had been in love with d:had fallen in love with fallen Fallen fallen fallen Fallen 英语翻译The low statistical significance of the two four-way combinations may be due to the small number of cases with that particular combination of treatments.Other four-way interactions had too few cases to attempt any statistical analysis. The Chinese mainland 60 new cases of A/H1N1The Chinese mainland ()60 new cases of A/H1N1 flu from 6 pm Friday to 6 pm Saturday,bring the total to 678.A.confirmedB.is confirmedC.had confirmedD.has been confirming