＿＿＿at the hotel ,they had a hot bath .

选B on arriving 强调某个时间点
On arriving at the hotel ,they had a hot bath.
一到旅馆,他们就洗了个热水澡。

B. On arriving = 在到达目的地时。 也可以写，Upon arriving

答案为：B!!!!!
在...时候; ...之后立即
on arriving home
刚到家就...

表达意思同as soon as,一....就.....

As soon as his father went out, the boy ran to the cinema.
爸爸刚出门, 那男孩就跑向电影院。

the moment......,一....就.....

例句：I found myself in an entirely new world the moment I arrived in Beijing.
我一到北京就感到耳目一新。

The answer is Boy!
On+Ving :表示“一……就……”

正确答案上面的天涯孤寡已经说了,支持他!!!

这里要用 On arriving 表示他们一到宾馆就洗了个热水澡。
On doing ...... 一...... 就.....

类似的还有：when....
scarcely.......when......
no sooner.......than......