或者：have difficulty with sth(with +名詞） have difficulty with English; 此句中 what struggling students are having difficulty with ( =struggling students are having difficulty with what . struggling students 現在分詞修飾students 意思為：在掙紮的學生們/糾結在難點處的學生們。
2.made it in the end (=succeed in the end 最後成功了）didn't explain to us 沒向我們解釋
what difficulty he had had working out the problems (have difficulty doing sth句型，此處用了過去完成時had had difficulty doing sth。 working out the problems : work out 是個詞組，表示： 弄明白，計算出，解決，解答....
句子的意思是：他最後終於成功了。但他沒有向我們解釋他曾經歷了何種艱辛才解決的這個問題。
had had difficulty working out ...之所以用過去完成時，是因為“經歷艱辛解決問題”發生在explained (過去時）之前。
3. Mary is said to have worked in the supermarket for 5 years.表示：據說Mary 過去曾經在超市工作過5年。...is said+to have done(不定式的完成形式）意思為：據說某人曾經幹過什麽/ 據說某人已經幹了什麽。例如：Peter is said to have studied in France for three years..據說Peter曾經（以前）在法國學習過三年。 He is said to have invented the first iphone.據說是他當初發明的第壹個iphone 手機。又如：Peter is said to have left China.據說Peter已經離開了中國。
.....is said to have been doing 的意思是：據說某人壹直在做某事；因此答案A的意思是：據說Mary到現在壹直在超市工作，已經有5年時間了（後面的句子又說“她上個月辭職了”，所以A不對。）
4. Everything his teach said was easily understood.(= Everything that his teacher said was easily understood. 句子的主幹為Everything was easily understood.是被動語態的句子，不能用不定式；his teacher said 是定語從句，定everything。
5. the same as 是固定搭配，表示：與...相同 the same dress as she is wearing 與她穿的裙子
樣式相同的裙子。 the same that.....也有此種搭配，意思是：同壹個 the same dress that she is wearing 的意思是：她身上穿的那條裙子（而不是：與她的裙子相同的裙子）
例如：I will buy the same dress as she is wearing. 我要買條和她穿的相同的裙子。
I will buy the same dress that she is wearing. 我要買她身上正穿著的她的裙子。
6. 這是壹類特殊句型，在此類句型中後面的不定式，不需要用被動。這類句型口語裏很常見，例如：The house is comfortable to live in. English is easy to learn. The book is difficult to read.
The question is easy to answer. The article(文章）is difficult to understand. The picture is beautiful to look at. The road is icy (冰的；滑溜溜的）to drive on. Hills and streams are good to look at. They are better (good的比較級）to look at than concrete buildings.
這類句型通常是： 某個東西+is（are，was...）+形容詞+不定式（主動）
如：這椅子坐著很舒服。 The chair is comfortable to sit on. (不用 to be sit on)
這張畫看著很賞心悅目 The picture is pleasant to look at.(不用to be looked at)
只是在這個特殊的句子結構中不定式才不需要用被動的，盡管的確有被動的意思。特殊事物特殊對待吧。
7. 這也是個特殊結構。妳是否還記得那樣的句子：There is nothing to do.沒什麽事兒可幹的。
There is nothing to eat. 沒有可吃的東西。/沒東西吃。There is no book to read. 沒有書可讀。
疑問句：Is there anything to eat? Is there any to drink? 此類結構中不定式通常可以用主動，盡管有被動的意思，卻可用主動來表示。
Anything to follow. 實際上是Is there anyting to follow ?的省略形式
啰啰嗦嗦說了很多，不知是否清楚。