The teacher asked the boy to read the text -- to the whole c

应该选 B
aloud , loud 和 loudly 都可以表示“大声地”,但在用法上有区别.
aloud , loud二者作为副词,都有“大声地”、“响亮”的意思,有时可以通用.但aloud与read,think连用时,表示“出声”,而loud用于talk,speak,shout,laugh等动词之后,在口语中代替loudly
① aloud 强调发出的声音能被听见,意思为“出声地”或“大声地”,常用 read , call 等动词连用.例如：
Please read the text aloud.
请朗读一下课文.
② loud 意为“响亮地”、“大声”或“高声地”,侧重发出的音量大,传得远,一般多用来修饰 speak , talk , laugh 等动词. loud 还可用作形容词.例如：
Speak louder, please, or no one will hear you.
请大声些,否则没人能听见.
③ loudly 意为“响亮地”,其基本意义与 loud 相同,还常与 ring , knock 等动词连用. loudly 放在动词前后均可,含有“喧闹”或“嘈杂”的意味.例如：
Suddenly the bell on the wall rang loudly.
突然,墙上的铃大声地响起来.
aloud, loudly只能用作副词；loud既可作副词,也可用作形容词.当副词用时,loudly与loud一样用来说明声音的强度,意思是"高声地,喧噪地",只是在动词后面loud比loudly更常用些.他们的反义是：quietly.例如：
Don't talk so loud (loudly)----you'll wake the whole street. 别那么大声说话,你快把左邻右舍都吵醒了.
Someone knocked loudly (loud) at the door. 有人在大声敲门.
注：而aloud往往与动词read和think连用,表示真的把话说出,而不是在脑子里默默地"说".
She has a very good pronunciation when she reads aloud.她朗读时,发音很好.