1.It is...to do sth：做某事是....
解析：It 是形式主语，后面一半接形容词做表语，to do sth是不定式短语作真正主语。
2.make do和make doing是两种表达方式
解析：make、have、let三个为使役动词，其后跟省略to的不定式作宾语补足语，即：makehavelet sb. do sth.（让某人做某事），例如:The teacher made him wait outside.(主动语态)
在被动语态的句子中，则要还原不定式的符号to，即：He was made to wait outside.
也有makehave sb. doing sth.的结构，意思为：让某人一直做某事，强调动作的持续性。例如：The boss made the workers working from dawn to dark.(老板让工人们从黎明一直工作到天黑.)
另外还有makehave sth. done,指让别人帮助完成某事，例如：He madehave his bike repaired.(他让人帮他修理自行车.)
make something to do 还是make sth do?
make something do sth 主动语态时,make something do sth,see sth do,let sth do等是省去了to的不定式,习惯用法是这样,不用to do,答题时用to do是错的,如：He makes the dog wait. 被动语态时,make sth do,see sth do,let sth do等要还原出to,就用be made to do,如：he is made to wait 他被人要求等待 总的来说不用make sth to do,只有主动语态的make sth do和被动语态的be made to do.
3.英语中,有avoid sth和avoid doing sth,没有 avoid to do sth.
它们意思一样,都是“避免.”的意思,只是avoid sth接的是名词或代词,avoid doing sth 接的是动名词.如adoid the accident“避免事故”,advoid being injured“避免受伤”.
4.turn to
to是介词（多数是这个意思）, (使)转向；(使)变成；求助于；翻书到，turn to sth./v-doing也就是动名词形式,实际上还是名词。
turn to sth/ turn to doing sth 开始干… e.g He turns to the homework.He turns to doing the homework.
另,turn to sth 也有“求助于”意思 e.g you can turn to your teacher when you have troubles
to是不定式（除了轮到.转向到.） It 's your turn to tidy up the room . 这回该你收拾房间了相当于It‘s your turn to do sth.
5.“被认为，视为”的几种表达：
be counted as 被视为
be regarded as 被视为
think that 认为
deem 认为，视为
consider as 考虑
treat as 治疗
如：treat A as B 把A当作B对待
regard A as B 把A当作B看待
6."反之"的几种表达：conversely; otherwise; contrarily; on the contrary; contrariwise; whereas;
7.because和because of的用法区别
because是连词,其后接原因状语从句或回答以why开头的问句；
如： He is called Mitch, because his name is Mitchell. 人们叫他米奇，因为他大名叫米切尔。
because of是复合介词,其后接名词、代词或动名词,或者what引导的名词性从句等。
如： We could see him wasting away because of his illness. 我们看得出他因为生病而日渐消瘦。
（未完待续）