Класть (положить) / ставить (поставить) 

As all the four verbs mean "to put", it's quite difficult for a Russian learner to distinguish between them.

Класть (положить) means "to put something horizontally":

Положи книгу на стол. - Put the book on the table.

Куда ты обычно кладешь хлеб? - Where do you usually put bread?

Ставить (поставить) means "to put something vertically, usually on a hard surface":

Куда ты поставил бутылку? - Where did you put the bottle?

Поставь книгу на полку.  - Put the book on the shelf.

You might also be asking yourself what's the difference between "класть" and "положить"? "Ставить" and "поставить"?

"Класть" and "cтавить" are imperfective verbs, while "положить" and "поставить" are perfective verbs. That means that you use "класть" and "cтавить" while talking about repeated or unfinished actions:

Когда я работала за этим столом, я всегда клала мою сумку сюда.  - When I worked at this table, I always used to put my bag here.

Когда мы жили в деревне, мы ставили обувь перед входной дверью. - When we lived in the country, we used to put our shoes in front of the entrance.

Когда я ставила книгу на полку, зазвонил телефон. - When I was putting the book on the shelf, the phone rang.

 "Положить" and "поставить" are normally used for actions that happen once:

Петр положил мобильник в карман. - Peter put the mobile phone into his pocket.

Мы поставили стаканы на стол. - We put the glasses on the table.

Please, note:

1. The verb "ложить" doesn't exist.

2. The verb "покласть" doesn't exist either.

3.  In the present, we always use "класть" and "ставить":

Я всегда кладу молоко сюда. - I always put milk here.

Куда вы обычно ставите стулья? - Where do you usually put chairs?

4. In the imperative form, we usually use "поставь" and "положи":

Положи руки на колени. - Put your hands on your lap.

Поставь книгу на полку. - Put the book on the shelf.

Now you can do the exercise.