Kate is a school girl. She got many presents on her _______ birthday.
A:nine
B:the ninth
C:ninetieth
D:ninth
在比例尺是1:4000000的地图,量得A、B两港的距离9厘米,一艘货船于上午6时以每小时24千米的速度从A港开向B港,到达B港的时间是____.