21.had better, would rather 后跟不带to的不定式。

F:You had better to pay attention to the details.
T:You had better pay attention to the details.
F:I had better not to play tennis this afternoon.
T:I had better not play tennis this afternoon.
F:Which movie would you rather to see?
T:Which movie would you rather see?
F:She says that she would rather not to have dessert.
T:She says that she would rather not have dessert.

22.In,into,In意指location within.Into指motion or direction。

F:She stepped carefully in the car.
T:She stepped carefully into the car.
F:He jumped off his bicycle and ran in the library.
T:He jumped off his bicycle and ran into the library.

23.in regards to为误用, 应说in regard to,as regards, 或 regarding.

F:I am writing in regards to your letter of May 10.
T:I am writing in regard to (or as regards, regarding) your letter of May 10.

24.in spite¹ of,despite都是介词,后面不跟从句。

F:I was able to concentrate despite the room was noisy.
T:1 was able to concentrate despite the noisy room.
F:Tn spite of it was cold, he didn't wear a coat.
T:In spite of the cold, he didn't wear a coat.

25.Its,it's;Its是代词所属格,It's 是 it is的缩略式。

F:Us essential that we leave on time.
T:It's essential that we leave on time.
F:The human body and it's organs are interesting to study.
T:The human body and its organs are interesting to study.
F:The dog wagged² -it's tail when it saw the food.
T:The dog wagged its tail when it saw the food.

26.kind,sort,和type都是单数,只能被单数形容词修饰,其复数形式分别是kinds,sorts,和types.

F:You should avoid making these kind of mistakes.
T:You should avoid making these kinds of mistakes.
OR
You should avoid making this kind of mistake.
F:Those kind of insects are harmful to man.
T:Those kinds of insects are harmful to man.
OR
That kind of insect is harmful to man.

27.kind of a,sort of a,type of a.省略a。

F:What kind of a telephone did the company install?
T:What kind of telephone did the company install?
F:The vicuna is a shy type of an animal.
T:The vicuna is a shy type of animal.

28. later, latter. Later是late 的比较级，指两个人或两件事物其中的后者

F:Jefferson and Lincoln are two famous presidents. The later was assassinated³ while in office.
T:Jefferson and Lincoln are two famous presidents. The latter was assassinated while in office.

F:I always lay down after I eat dinner.
T:I always lie down after I eat dinner, (present tense)
F:He laid down because he had a headache.
T:He lay down because he had a headache, (past tense)
F:The books are laying on the table.
T:The books are lying on the table, (present participle-)
F:The teacher lay her books on the table when she entered the room.
T:The teacher laid her books on the table when she entered the room, (past tense)
F:The boys have laid under the trees for hours.
T:The boys have Iain under the trees for hours, (present participle)

30.lend,loan.Lend是动词;loan是名词。

F:Would you mind loaning me your pencil?
T:Would you mind lending me your pencil?
F:I needed money, so John loaned me some.
T:I needed money, so John lent me some.