Which of the following statements is not correct with regard to a mathematics textbook.

Correct option is C

A mathematics textbook should not have solved examples only. While solved examples are important to show students how to apply concepts, they should not be the only type of exercise in the book. Students also need to practice solving problems on their own in order to develop their problem-solving skills.
The other three statements are all correct. A mathematics textbook should not be too thick or heavy, as this can make it difficult for students to carry and use. It should have varied exercises to give students practice with different types of problems. And the examples in the book should be related to the daily lives of the students, as this will help them to see the relevance of mathematics to their own lives.
Therefore, the answer is (c).