第一个：convince有两个用法：

He convinced me of his innocence.

他使我相信他是无辜的。

I was convinced that he knew the truth.

我确信他知道事实。

如果后面没有that，那就选A Convincing ，原句也可以这样说:Convincing the government can lead them out of the financial crisis, people are optimistic about the future of the country. .

因为有that所以就省略了主、谓，其实完整的应该是People are convinced that...

第二个：如果你理解这名话的意思就知道为什么选 B了，是说他会说起_当_他适应这个新国家时所遇到的困难。重点是【当。。时】，困难是和适应这个新国家时发生的 ，完整的说法是he would talk about the great difficulty he had 【when he was 】settling______in the new country。

settle in

适应(或习惯于)新环境等

第三个：be wise to do / not to do sth固定用法