11-15. smooth.

[X is smooth.] = The surface of X feels like this: When you rub this surface using your hand, all the parts of the surface feel the same, and you do not feel parts that are high or low more than others. Because of this, you can move your hand easily when you rub X.

[Below the surface of the water, I found a smooth round stone.]

11-16. school, schools.

[X is a school.] = X is a place where people help other people learn things.

[Children need schools because this is where they learn to read and write and count.]

11-17. lead, leads, to lead, leading, led.

[You lead X.] = X is a group of people. The people inside this group do the things you tell them to do, because they think the things you tell them are important and likely to be good for the group.

[Someone needs to lead this group of people and tell them what to do.]

11-18. book, books.

[X is a book.] = X is a group of pieces of paper that are connected. There are many words or pictures on the surfaces of these pieces of paper. Part of each piece of paper is connected to all the other pieces. A person can hold X and look at the words and pictures on the surface of each piece of paper.

[I bought a book that I want to read.]

My school helps me learn to read and write.

My school gave me __________.

• these books to read
• these books to taste
• these sheep to lead