答:sth.is being frozen.是某物正处在冷冻这个过程中.比如你将肉放进冰箱的冷冻室里,在一个小时之内,It is being frozen.
而sth.is frozen.是系表结构,过一个小时之后,你将那肉拿出来,It is frozen.
这里候的frozen已经成为一个形容词了.表状态.
原题句是形容词(过去分词)作状语,表示主语(the old man)的情况.相对于:As he was almost frozen,the old man could not get off the ground.
如用being frozen,则为一被动动作,相当于:As he was almost being frozen,the old man...
不对.