Seeing his father coming,the boy was very afraid and_______his head

B。
dare do sth 的否定形式是dare not do sth。
dare to do sth 的否定形式是 didn't dare to do sth。
两者意思是一样的。只是用法不一样。因此排除A, C, D三个选项。

dared not to raise
习惯说法

b
dare做情态动词，用法dare do sth / dare not do sth
dare还做一般动词，用法dare to do sth /didn't dare to do sth

看到他父亲来了，他害怕得不敢抬起头。

b
dare做情态动词时用法为dare do sth否定为dare not do
做实意动词时是dare to do sth否定为do not dare to do sth