问题
It is really crazy ________ Peter to let his ________ son swim alone in the river.
A:for; 5 years old
B:of; 5 years old
C:for; 5-years-old
D:of; 5-year-old;
B:of; 5 years old
C:for; 5-years-old
D:of; 5-year-old;
正确答案是：
