问题补充：
These flowers should not be watered too , once .
A. long; every other day
B. often; every fourth day
C. soon; every two days
D. frequently; each five days
答案：
A. long; every other day
(答案→)B. often; every fourth day
C. soon; every two days
D. frequently; each five days
解析： long长；soon 快；often经常；frequently频繁；every fourth day/every five days每5天，每隔4天。句意：这些花不能被经常浇水，每四天浇一次就行了。本题的一空不能使用long, soon与句意不配。故B正确。
