改否定句、疑问句、肯定句，有没有什么好的方法？

根据实际情况回答问题：
how often do you have a P.E lesson at scool? once a week.
when is your birhday? August 1st.
how much is your schoolbag? CNY 1800.
what day is today?(这题目好像出错了）Tuesday.(没错，这个是问星期几，what day is it today是问几号)
what clothes are you wearing?t-shirt.

这个对吗？-- 错的改掉了，其他都可以的。
Which is your favorite city, Shanghai, Guangzhou, or Beijing?
Your sister is a doctor or a teacher?
You usually at 11:00 or at 12:00 for lunch? -- 没动词。you usually have lunch at 11 or 12?
Which class are you, a group or a second class?--少了个介词，如果按你写的把它变成陈述句就是you are which class，检查对不对可以变成陈述句看看，陈述句比较容易看出问题。which class are you in, Class 1 or Class 2?
Who is this cat, his or her?-- 同学，你写的陈述句会变成this cat is who（这只猫是谁，而不是“谁的”，谁的应该用所有格的疑问代词whose，后面的应该用his/hers名词性物主代词），应该是whose cat is this, his or hers?
What do you want, sandwiches or hamburgers?

前面的改否定肯定句真心没看懂，后面的肯定否定是什么意思。。。

楼主好，您答的不全对，正解如下。
Which is your favorite city, Shanghai, Guangzhou, or Beijing?
Is your sister a doctor or a teacher?
Do you usually eat lunch at 11:00 or at 12:00 ?
Which is your class , class1 or class2?
Whose is this cat, his or hers?
What do you want to eat, sandwiches or hamburgers?

Twice a week.
March 1st.
150yuan.
Friday.
My school uniform.

望采纳。