24.\x05He\x05always keeps calm\x05 difficulties an danger.

B
这个介系词表示面对,其余三项不贴切.
C
remember后接动词不定式表示动作未做,动作已做,接动名词.
D
在基数词、neither、all、none、most、one、形容词最高级、一些名词如part、the minority、the majority、the privelege few等后面,常常用of which或of whom来引导非限制性定语从句.因为是在介系词of后面,所以只能用which或whom.而且这里的of whom、of which是不用whose来代替的,在别的名词后的of whom、of which则可以用whose代替.比如：
He bought some apples,two of which he gave her.
I have twenty-one members in my club,most of whom are girls.
John gave several reasons,only a few of which were valid.
I met some girls,one of whom is my cousin.
The teacher discussed Jim,one of whose problems was poor study habits.
I have twenty-one customers,the privilege few of whom can affiord it.
It is a family of eight children,all of whom study music.
We tested fifteen samples,none of which was completely waterproof.
He is looking for a car the engine of which was in good condition.（这句话的the engine of which则可以用whose engine来代替）
D
先行词被形容词的最高级修饰时,关系代词只能用that,不能用which,少用who、whom.
C
inclined后面加动词不定式,表示愿意.
D
afford在这里是动词,表示负担得起,后面接动词不定式,其余三项不贴切.
D
在这里,switch可以表示调换的意思.
紧急关头
把……视为理所当然
盛衰沉浮
有规律地,定期地
突然
与……协调一致
好歹
提前开始
所有其他的事情都是平等的（这是分词的独立主格结构）
希望我能帮助你解疑释惑.