A:Had; met ; was driven
B:Have; met; has drive
C:Have ; met; was driven
D:Did; meet; had been drive
某单位为绿化环境,移栽了甲、乙两种大树各2株,设甲、乙两种大树移栽的成活率分别为23和12,且各株大树是否成活互不影响,在移栽的4株大树中,两种大树各成活1株的概率为____