(1)I'm wondering (who) he expects will win the gold medal in

(1)I'm wondering (who) he expects will win the gold medal in Men's single.
此题为什么选择who而不是选择whom
(2)You'd better nake mark (where) you have any questions.
为什么用where.
(3) (Had it not been) for the doctor's careful treatment,he (couldn't have lived) till last year.

(1)首先明确,he expects的宾语的确是who,但是这个who在充当expect这个词的宾语的同时,还充当who will win the gold medal in Men's single这句从句的主语,因此只能用主格形式,而不能用宾格形式whom.
（2）You'd better ask mark where you have any questions.
划分句子成分的话,you 是主语,谓语 had better ask,宾语 mark,主谓宾都全了,不缺名词性成分,因此排除了名词性从句的可能性,那么不是定语从句就是状语从句.
假设是定语从句的话,从句修饰先行词,但是显然,you have any quesions与前面的Mark不够成修饰关系,因此又排除定语从句的可能性.
因此做状语从句,填where交代主句发生的地点,你在有问题的地方最好问一下马克.
注：状语从句可以与定语从句互相转换
You'd better ask mark where you have any questions.
= You'd better ask mark at the points where you have any queions.
(3）这是虚拟语气的用法.if 被省略的倒装结构,正常的表达应该是
If it had not been for the doctor's carefull treatment,he couldn't have lived till last year.
用if条件从句表示的虚拟条件,是虚拟条件最普通的方式.
① 虚拟现在时表示与现在事实相反的假设,其if 从句的谓语形式用动词的过去式(be 一般用were),主句用would/ should/ could/ might +动词原形,例如：If I were in your position I would marry her.
② 虚拟过去时是表示与过去事实相反的假设,if 从句的谓语形式用过去完成时即had＋过去分词,主句用would / should / could / might + have +过去分词,例如：If it had not rained so hard yesterday we could have played tennis.
③ 还可以表示对将来的推测,由于是将来还没有发生的,所以谈不上是真实的还是虚假的,只能说这个事情发生的可能性有多大.一般情况下,可以用陈述语气的if从句来表示对一个未来事实的推测,这个事实是完全可能发生的.If从句的谓语形式用一般过去式或用were to / should +动词原形,主句用would / should /could/ might +动词原形,例如：Jean doesn't want to work right away because she thinks that if she were to get a job she probably wouldn't be able to see her friends very often.
有时可以把含有助动词、情态动词、be或have的虚拟条件句中的连词if 省去,而将had ,should,were 等词提到主语之前,即用倒装结构,这时候,如果出现not等否定词,否定词需放在主语后面.这种结构在口语中很少使用,但频频出现在各类考试中出现,例如：If it had not rained so hard yesterday we could have played tennis.→Had it not rained so hard yesterday,we could have played tennis.