$*OwO:$

  + Diễn tả một sự việc hiển nhiên.

$-$ Câu điều kiện loại $I$: If + S + V (s/es), S + will/ shall/ can/ may/ should/ must + V (Bare).

  + Diễn tả một sự việc có khả năng xảy ra ở hiện tại.

$-$ Unless = If not (Nếu không, Trừ khi): Unless + S + V (s/es), S + will/ shall/ can/ may/ should/ must + V (Bare).

  + Mang ý phủ định nhưng được dùng trong câu khẳng định.

$--------$

$1.$ If you don't get the visa, you can't visit the USA.

$2.$ We can only get into the house if someone has key.

$3.$ unless you keep your feet dry, you will catch a cold.

$4.$ If Joean doesn't find a good job before September, she will stay on at school.

$5.$ Unless it rains soon, millions of pound's worth of crops will be lost.

$6.$ Unless you work hard, you'll ail the exams.

$7.$ If you don't save some money, you won't be able to buy the house.

$8.$ Unless you behave yourself, your parents will be very unhappy.

$9.$ If you don't have your hair cut, they won't let you in.

$10.$ Unless you do it carefully, you will feel sorry afterwards.

$11.$ If you don't ask him, he won't offer to help.

$12.$ Unless you go out more often, youll fail ill.

$13.$ Unless you take a hat with you, you'll be caught in the rain on the way back.

$14.$ If you don't write it again more carefully, he won't be able to read it.

$15.$ Unless you have another look at those lessons, you'll get bad marks.