The_of_which we had heard came from the children downstairs.何解呀

D
我们听到的楼下孩子的声音.

sound是声音的意思,voices也是声音,不过特指是什么什么的声音.所以不可以选A,因为不通顺.Noises是噪音的意思,名词,选B也不通顺.C也不行,道理和A一样.所以看来看去只有D合适.

voice

n.
1. 声音;嗓子[C][U]
He talked of his trip to HongKong in a cheerful voice.
他兴高采烈地谈了他的香港之行。
2. 表达的意见,愿望[S1]
3. 发言权[S][U][(+in)]
I have little voice in the matter.
我对此事没有多少发言权。
4. 代言人[S1]
5. 【语】语态[S1]
6. 【语】有声单音[U][C]

sound1

n.
1. 声音,响声;【物】声[U][C]
We heard sounds of laughter from the next room.
我们听到隔壁房间传来的阵阵笑声。
2. 喧闹声[C]
The sounds from the next room woke up the child.
隔壁房间传来的喧闹声把孩子弄醒了。
3. 音调;【语】音[C]
4. 可听范围,听距[U]
We camped within sound of the sea.
我们在听得见海涛声的地方露营。
5. 感觉,印象[U][C]
6. 【俚】流行音乐[P1]
7. 【俚】唱片[P1]

noise

n.
1. 声响;喧闹声[C][U]
What's up? There's such a loud noise in the corridor.
出什么事啦?走廊里喧闹声那么大。
2. 噪音,干扰[U]
3. 议论[C][U]

第二个空格在哪里啊？