kilometer是可数名词吗

　　Then he and his wife entered a five-kilometer race.

　　后来，他和他的妻子参加了5千米的比赛。

　　You get that out of 1 cubic kilometer of seawater.

　　你能从一千立方米海水中得到这么多。

　　The mine is some 840 meters deep and 6.5 kilometer long.

　　这个矿区有840米深，6.5千米长。