阅读《虞美人①》词，回答相关问题
春花秋月何时了，往事知多少。小楼昨夜又东风，故国不堪回首月明中。雕阑玉砌应犹在，只是朱颜改。问君能有几多愁，恰似一江春水向东流。
【注】①一般认为，《虞美人》是词人入宋做俘虏的第二年（977）或第三年（978）正月所写。

⑴若 $\overrightarrow{a}$ 是单位向量， $\overrightarrow{b}$ 也是单位向量，则 $\overrightarrow{a}$ 与 $\overrightarrow{b}$ 的方向相同或相反；

⑵若向量 $\overrightarrow{AB}$ 是单位向量，则向量 $\overrightarrow{BA}$ 也是单位向量；

⑶两个相等的向量，若起点相同，则终点必相同．

正确的个数为（   ）

    We're staying with Lingling's uncle in Hunan Province, and I'm having ____ (冠词) wonderful time here in Zhangjiajie. It's a magic land of mountains, forests and ____ (river). It's very large, about 480 square kilometres. It's famous  ____ (介词) the strange shape of its tall rocks. Some of them ____ (look) like humans while others look like wild animals. Last night we camped by a small lake. During the night, we____ (hear) a noise! It woke everybody up. We thought somebody  ____ (be) moving about. Lingling's uncle said it was an animal. We came out without  ____ (make) any noise, ____ (连词) found it was just a hungry monkey looking for food. This morning, we climbed Mount Tianzi! From the top we hoped to see the lakes and forests. But it was a pity that it was____ (cloud). We could only see the mountain tops above the clouds. Tomorrow we're going to Dongting Lake, ____ (冠词) second-largest freshwater lake in China. We'll be back home next week! Wish you were here.

甲在足够长的有水自来水管一端打击一次，乙在另一端用耳朵伏管听，能听到（   ）