Two little boats without any sails

1、What makes opening piano so hard?

為什麼鋼琴蓋很能開啟?

2、Two little boats without any sails，With ten passengers on do not go on the river or sea,But travel on dry the day the boats pass to and fro,But at night they are both empty.

有兩隻載著十個乘客沒有風帆的船，它們不再河裡或者海里航行，卻在陸地行走，在白天它們往往返返，在夜晚他們都是空的。它們是什麼呢?

　　答案：

1、because all the keys are inside 因為所有的鑰匙都在裡面

key：鍵，鑰匙

2、a pair of shoes 一雙鞋