尊敬的刘老师：你好！
有这么一道题：
I have many friends to ________ when I have trouble.
A. talk to B. talk C. talk about
我觉得选A，可是答案是C。请你帮助剖析一下，谢谢。
有这么一道题：
I have many friends to ________ when I have trouble.
A. talk to B. talk C. talk about
我觉得选A，可是答案是C。请你帮助剖析一下，谢谢。
从语法上角度，A/C都正确，因此需要从语义上进行筛选了.
I have many friends to talk to when I have trouble.
参考译文：当我有困难的时候，我有不少朋友可以进行倾诉。
=When I have trouble, I can/ will talk to many friends.
参考译文：当我有困难的时候，我可以/会向不少朋友倾诉。
I have many friends to talk about when I have trouble.
参考译文：当我有困难的时候，我有不少朋友可以进行谈论/讨论。
=When I have trouble, I can/will talk about many friends.
参考译文：当我有困难的时候，我可以/会谈论/讨论/说到不少朋友。
（备注：以上不定式的逻辑主语为句子主语，不定式与被修饰词存在逻辑上动宾关系.）
解答如下：
以上为不定式作后置定语使用方法
talk to 侧重于一个人对另外一个人讲话.A talk to B,即A对B说话，强加直接和某人说话。
She was talking to a friend.
她正在跟一个朋友讲话。
Ive asked you not to talk to that rough boy!
我说过叫你别和那粗野的小子说话!
A good newspaper,I suppose, is a nation talking to itself.
我觉得反映民族心声的报纸才是好报纸。
Donttalk tome about that fellow.
别跟我谈起那个家伙。
Its often helpful during an illness totalk toother sufferers.
病中与同病者谈天常是有益的。
He disdained that man for snobbishness and was unwilling totalk tohim.
他鄙视那个势利小人，不愿和他说话。
They taught the little boy not totalk tostrangers.
他们教育小孩子不要和陌生人说话。
She detests having totalk TOPeople at parties.
她讨厌在宴会上为应酬而和人交谈。
He was too shy totalk toanyone at the party.
在晚会上他非常害羞，没和其他人讲话。
Donttalk tome like that!
别那样和我说话！
talk about 谈起/谈到某人/某事.强调间接谈论/说到/讨论某人/某事。
I have some very important business to talk about.
我有要紧的业务想谈。
What are you talking about?
你们在讨论什么?
Lets talk seriously about your future.
咱们认认真真地谈谈你的以后吧。
I talked yesterday about the problems facing young people in todays society.
昨天我讲了当今社会年轻人人所面临的问题。
We talked about what to do.
大家讨论该如何解决。
I nevertalk aboutgossip.
我从不传播流言蜚语。
Please donttalk aboutit in front of the children.
请勿当著孩子们谈论那事。
Dont sentimentalize when youtalk aboutanimals.
谈论动物不必忧形於色。
Steve and Jack gave atalk abouttheir trek across the Polar ice cap. It was very interesting but it made my hair stand on end just to hear about the dangers they faced.
史蒂夫和杰克讲述了他们在极地冰盖的一段艰苦跋涉，故事津津有味，只不过听到他们遇见种种险情时，我吓得非常。
We cantalk aboutthis matter in private.
大家只能私下谈论这个话题。
